Dissertation_residential Buildings on Sloping Sites

DISSERTATION ON

RESIDENTIAL BUILDINGS ON SLOPING SITES

Submitted By: Deepa Sharma Scholar Number: 101110047 Eighth Semester B. Arch.

Subject Coordinator: Prof. Manmohan Kapshe

DEPARTMENT OF ARCHITECTURE AND PLANNING MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY, BHOPAL

MAY 2014

MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY, BHOPAL DEPARTMENT OF ARCHITECTURE AND PLANNING

DECLARATION

This dissertation, entitled ‘RESIDENTIAL BUILDINGS ON SLOPING SITES’ is  being submitted in subject in ‘ARC 426, Research Principles and Dissertation’ Dissertation’ as part of requirement for eighth semester of Bachelor of Architecture by the undersigned for evaluation. The matter embodied in this dissertation is either my own work or compilation of others’ work, acknowledged properly. If, in future, it is found th at the above statement is false, then the institute may take any action against me as per rules.

Deepa Sharma Scholar Number: 101110047 May 2014

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MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY, BHOPAL DEPARTMENT OF ARCHITECTURE AND PLANNING

DECLARATION

This dissertation, entitled ‘RESIDENTIAL BUILDINGS ON SLOPING SITES’ is  being submitted in subject in ‘ARC 426, Research Principles and Dissertation’ Dissertation’ as part of requirement for eighth semester of Bachelor of Architecture by the undersigned for evaluation. The matter embodied in this dissertation is either my own work or compilation of others’ work, acknowledged properly. If, in future, it is found th at the above statement is false, then the institute may take any action against me as per rules.

Deepa Sharma Scholar Number: 101110047 May 2014

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ACKNOWLEDGEMENT

I would like to gratefully and sincerely thank Dr. Manmohan Kapshe for his guidance, understanding, patience, and most importantly, his friendship during my dissertation research study. He encouraged me to grow as an instructor and an independent thinker. I am not sure many graduate students are given the opportunity to develop their own individuality and self-sufficiency by being allowed to work with such independence. The writing of this dissertation has been one of the most significant academic challenges I have ever taken. Though the following dissertation is an individual work, I could never have reached the heights or explored the depths without the help of  books published by various authors, the e-books available on the internet, the research  papers published by various authors and the various organizations and websites  providing information related to my dissertation topic. My very special thanks to my colleagues for their support and suggestions for my research and all the other respective sources for helping me.

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LIST OF CONTENTS DECLARATION ....................................................................................................... I ACKNOWLEDGEMENT ........................................................................................ II LIST OF CONTENTS .............................................................................................. II LIST OF FIGURES .................................................................................................. V LIST OF TABLES ................................................................................................. VII Chapter-1.

INTRODUCTION ...................................................................................1

1.1.

Justification .....................................................................................................1

1.2.

 Need of the topic ............................................................................................. 2

1.3.

Aim .................................................................................................................. 3

1.4.

Objectives ........................................................................................................ 3

1.5.

Scope ...............................................................................................................4

1.6.

Limitations ......................................................................................................5

1.7.

Methodology ................................................................................................... 6

Chapter-2.

UNDERSTANDING

THE

TOPOGRAPHY

OF

SLOPING

LANDFORMS AND DESIGN PRINCIPLES .............................................................. 8 2.1.

Types of sloping landforms ............................................................................. 8

2.2.

Buildings on slope: the implications and solutions ....................................... 11

2.3.

Clustering of houses ...................................................................................... 16

2.4.

Scenic opportunities ...................................................................................... 17

2.5.

Conclusion..................................................................................................... 18

Chapter-3.

BUILDING TYPOLOGIES, CONSTRUCTION TECHNIQUES AND

SERVICES 19 3.1.

Residential building typologies prevalent in North India ............................. 19

3.2.

Residential building typologies prevalent in North East India ..................... 20 III

3.3.

Construction techniques to be adopted while designing the building in

sloping sites..............................................................................................................21 3.4.

Roads: ............................................................................................................26

3.5.

Practical considerations (landslide or slope stability) ................................... 32

3.6.

Recommended practices ................................................................................ 35

3.7.

Conclusion..................................................................................................... 35

Chapter-4.

LANDSCAPING ON SLOPING LANDFORMS ................................. 36

4.1.

Planning a landscape on slope ....................................................................... 36

4.2.

Landscaping principles on sloping sites ........................................................ 39

4.3.

Ways of landscaping a sloping site ............................................................... 44

4.4.

Erosion control for residential hillsides ........................................................ 48

4.5.

Conclusion..................................................................................................... 51

Chapter-5.

CASE STUDIES OF DIFFERENT BUILDINGS ON SLOPING SITES 52

5.1.

Car park house, Los Angeles......................................................................... 52

5.2.

Family house, Prague .................................................................................... 53

5.3.

Apartment block, North-East Italy ................................................................ 54

5.4.

Stepped house, Spain.....................................................................................56

5.5.

Conclusion..................................................................................................... 57

REFERENCES ........................................................................................................58 ANNEXURE............................................................................................................ 60

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LIST OF FIGURES  Figure 2.1: Up slope (left) and Down slope (right) (Tweed Shire Council) ................. 9  Figure 2.2: Side slope (left) and Rolling slope (right) (Tweed Shire Council) .......... 10  Figure 2.3: Building on flat site (left) and moderate slope (right) (Tweed Shire Council)........................................................................................................................ 11  Figure 2.4: Building on steep slope (left) and extreme slope (right) (Tweed Shire Council)........................................................................................................................ 11  Figure 2.5: Design principles that must be taken care of (HRO) .............................. 15  Figure 2.6: Over excavation and creation of artificial plateau should be avoided (North Tipperary County Council, 2009) .................................................................... 15  Figure 2.7: Step building design (Tweed Shire Council) ............................................ 16  Figure 2.8: Standard large lot residential layout, mixed single family layout with open  spaces, mixed density layout with open spaces ( from left to right) (City of VernonHillside Guidelines 2008, 2008) .................................................................................. 17  Figure 3.1: RC moment resisting frame with unreinforced masonry infill walls (left) and open ground storey structure (right) (Assessment Project Group of IIT Bombay, IIT Guwahati, IIT Kharagpur, IIT Madras, IIT Roorkee, 2013) .................................. 20  Figure 3.2: Cut and fill construction (left) and stilts construction (right) Basements/Retaining walls (Tips for building on a sloped terrain, 2014) (How to Build on a Sloping Site) ............................................................................................... 22  Figure 3.3: Basement construction on sloping sites (Tips for building on a sloped terrain, 2014)................................................................................................................23  Figure 3.4: Typical retaining wall construction, Gabion wall and rock buttress (from left to right) (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS) ...........................................................................................................24  Figure 3.5: Common types of retaining structures (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS).................................................. 24

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 Figure 3.6: Construction detail for retaining wall of height upto 2 m (left) and 5 m (right) (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS).......................................................................................................................... 25  Figure 3.7: Typical rock wall construction for smooth backfill (left) and face with  steps (right) (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS) ...........................................................................................................25  Figure 3.8: Two lane road (left) and split level access road (right) (California Coastal Commission) ................................................................................................................ 27  Figure 3.9: Single lane road with pullouts (left) and bridge (right ) (California Coastal Commission) ................................................................................................................ 28  Figure 3.10: Culvert (left) and Arizona crossing (right)  (California Coastal Commission) ................................................................................................................ 29  Figure 3.11: Balanced cut and fill for most of the construction on hill slopes (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS) ....... 30  Figure 3.12: Full bench cuts for slopes exceeding 60% (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS) ................................... 30  Figure 3.13: Through cut (Slope Stabilization and Stability of Cuts and Fills- LOWVOLUME ROADS BMPS) .........................................................................................31  Figure 3.14: Typical fill (Slope Stabilization and Stability of Cuts and Fills- LOWVOLUME ROADS BMPS) .........................................................................................31  Figure 3.15: Benched slope fill with layer placement (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS).................................................. 31  Figure 3.16: Reinforced fill. These can be used as an alternative for retaining wall (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS) ...................................................................................................................................... 32  Figure 3.17: Through fill (Slope Stabilization and Stability of Cuts and Fills- LOWVOLUME ROADS BMPS) .........................................................................................32  Figure 3.18: Contour graded slope (left) and Steep geogrid slope (right) (California Coastal Commission) ................................................................................................... 34 VI

 Figure 4.1: Ground covers for steep slopes (Alders) .................................................. 42  Figure 4.2: Steep sidewalk grades are a significant barrier to access for many  pedestrians (left), If he side walk grade exceeds 5% level landings should be provide at regular intervals (right) (Federal Highway Administration, Updated: 02/10/2014) ...................................................................................................................................... 44  Figure 4.3: Gardens showing terracing (Washburn) .................................................. 45  Figure 4.4: Construction of tiered garden (Alpha Landscapes Design ltd.) ............... 46  Figure 4.5: Rock landscaping (DIY network) ..............................................................47  Figure 4.6: A sloping site, made up of semicircular layers. The key stone is the largest  stone. Subsequent stones get progressively shallower so that they disappear into the  ground at the sides of the site. (Rock Landscaping Ideas – Flat and Sloping Sites) ... 48  Figure 5.1: Car park house built on sloping site (ArchInspire) .................................. 52  Figure 5.2: Conceptual sketches developed by the architect   (Grido Architektura and Design) ......................................................................................................................... 53  Figure 5.3: View of the house (top), timber frame construction (bottom left), sections (bottom right) (Grido Architektura and Design) ......................................................... 54  Figure 5.4: The three-storey Dolomitenblick building (Plazma Studio) ..................... 55  Figure 5.5: Tiered home on sloping site in Spain (left), view showing arrangement of  spaces (right) (Eva Designs, 2014).............................................................................. 56  Figure 5.6: Side view of home showing stepped appearance (Eva Designs, 2014) ....56

LIST OF TABLES

Table 1 : Common stable slope ratios for varying soil/rock conditions (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS) ....... 60

VII

Table 2 : Relation between number of levels and number of gabions for flat backfill (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS) ...................................................................................................................................... 61 Table 3 : Relation between number of levels and number of gabions for face with  steps (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS).......................................................................................................................... 61

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CHAPTER-1.

INTRODUCTION

The housing we build today will not only help to shape our environment in the immediate future, it will also be determining the environmental quality of spaces. This study describes the contributions to quality and sustainability of the design of new residential developments on sloping sites. The context given in the report is aimed at achieving attractive and functional places through better design, better construction techniques and services, proper use of  building materials, suitability of landslopes for different buildings to promote: 1. The wider context of the local setting, the characteristics of the site for development 2. More sustainable patterns of living and working 3. More effective integration between topography and built up 4. The creation of attractive places in which people are happy to live, work and take their leisure. 5. Greater responsiveness to site and setting in the layout of new development to achieve a better balance between requirements and other factors. The creation of attractive residential environments with a genuine sense of place is a  prerequisite to achieving sustainability. The quality of where we live depends not just on the design of buildings, but on their layout and landscaping, the arrangements made for access, and in particular, how they relate to their surroundings. It is intended to encourage the interconnection of design considerations of the setting, landscape design, circulation patterns and buildings to form a coherent design structure.

1.1. Justification In global context, each and every piece of land should be praised to its individuality. At designing point of view, each site has got its own potential in terms of its richness, fertility, texture, ability to bear, nearby features like deep valleys, water bodies, hillocks, ridges and soaring mountains. Designing of building on sloping sites while avoiding the cut and fill construction techniques is cumbersome process because of change in ground levels. But spaces should be carved out respecting the character and physical behavior of site, thus 1

achieving the better functional space. These techniques are only employed when necessary. Designing on sloping spaces is a move away from typical standards of flat sites to a more integrated and functional approach to achieve high quality and sustainable designs. Most of the sloping sites due to its beautiful and admiring surrounding features, the user can enjoy the nature upto its full expanse. Spaces designed in sloping sites may differs from those of in flat or less sloping sites (where presence of contours can be neglected) in terms of their approach, dimensions, geometry, proportions, views, etc. Those spaces may prove inconvenient or exhaustive for physically challenged people, but that can also be avoided by following some design criteria, thus making the space more functional and universal. The execution principles, services utilized for construction of buildings are quite different from those adopted in flat sites. Also the ambient climatic conditions reaches extreme in most of the regions having uneven landforms. These places are also vulnerable to other natural calamities like seismic activities, storms, snowfall, hail, etc. Some of the buildings are constructed using locally available materials and techniques which may not be prevailing in other regions because there, the transport of building materials proves laborious. So, the study would help architects/ designers to get the complete idea of  perspective of spaces and designing according to the requirement of user and exploring the site upto its full extent.

1.2. Need of the topic 1. To understand the way that how spaces should be carved out respecting the site potential, field patterns, townscapes and landscapes. 2. To lessen the impact of seismic impacts, wind loads, and other dynamic loadings on building and its surroundings. 3. To design spaces according to the extreme of climat es 4. To minimize the cut and fill construction techniques, adopting sustainable and green building principles as far as possible. 5. To make the space more functional for physically challenged people. 2

6. Development designed to emphasis a sense of place and community with  proper movement networks. 7. Move away from conventional standards to more interesting approach for achieving high quality and functional spaces. 8. To enhance the importance of views and vistas. 9. Protection of existing trees and other important natural and topographical features. 10. Considers the wider context of the local setting, the characteristics of the site for development, and strategies for the overall design character of a proposal. 11. Giving guidance on the main elements needed to achieve high quality design, from the overall landscape and urban design considerations to the layout of dwellings, means of access and patterns of movement. 12. Integrate with existing patterns of movement.

1.3. Aim The main purpose of the study is to contribute to the methodologies and principles employed for carving out spaces in sloping sites. The study is also intended to contribute to the better understanding of terrain and opportunities for creating spaces which have greater responsiveness to site. To establish design principles for different typologies of residential buildings on sloping sites.

1.4. Objectives Residential development on sloping sites must complement the scenic hillside character by integrating unique or special natural features such as landforms, rock outcroppings, viable existing stands of trees and vegetation, ravines, water features, hilltops and ridgelines; protect wildlife habitat; avoid unstable or hazardous sites and  protect lives and property from hazardous conditions, such as rock falls, storm runoff, erosion, etc.; provide safe year round access for residents, visitors and service  providers; 1. Suitability of land slopes for different buildings and design crite ria

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Sloping landforms can be classified on the basis of direction of slope and amount of slope. Each site has its individuality on which a particular type of arrangement of spaces can be done. This further requires analysis of some of the other parameters. A thorough investigation and assessment of ground conditions and stability is essential to determine whether a site is suitable for building on, where the best place may be to locate a building and the type of structural system that will be required. 2. How sloping landforms can be best accomplished for getting functional and risk free spaces Sloping sites are generally prone to soil erosion, landslides, debris flow, seismic activities, etc. These are also burdensome for physically challenged people. But incorporating some of the design criteria, spaces can be made more functional and risk free. Natural character of the hillside should be preserved as well as provide scenic views from a hillside site. 3. Design principles, construction techniques, materials and services Design

solutions/construction

techniques

like

step

building

design,

cut/fill

construction techniques, raising the building on stilts/poles, retaining wall construction, drainage issues, seepage problems should be incorporated which respects the site potential upto its full expanse and lessen the impact of seismic loading and other dynamic loadings. 4. Scope of landscaping on sloping sites Landscapes on sloping sites will certainly take a little more thought and effort than for a normal flat site but the results can be very interesting by playing with change in levels, creating stepped appearance, terracing, tiering, etc. The biggest concern is usually the risk of erosion. Additionally, planting and maintaining plants on inclines can be a difficult undertaking. However, there are many ways to successfully landscape a slope and create an attractive incline.

1.5. Scope The study is intended for use in the design of all the proposals for residential  buildings of all typologies in global context having uneven terrains from small scale housing projects to major housing projects on large sites satisfying the climatic 4

conditions, culture and heritage of the region and also respecting the landform.  Nevertheless, the principles in the report will be used by architects as a basis for assessing any proposal. The study also have emphasis on landscaping features(decks, patios, pavers, pergolas, entryways, walkways, plants, retaining walls, lighting, water bodies, etc.), process of landscaping in slopes, hardscaping and softscaping. Preservation of slopes or hillside erosion control, importance of heights and  proportions, designing open spaces, protection of existing trees, and other important natural and topographical features is also included in report. Study also includes construction of houses using modern building materials and techniques as well as vernacular materials and techniques. The study also includes the construction technologies, materials, services (water supply, sewage disposal, gas, electricity, lighting and telecommunication) and study about vehicular and pedestrian networks. Seismic vulnerability assessment of building types is also included in study. Cost factors are not taken into consideration in this study. The study also not includes designing in largely steep slopes, inaccessible sites, places having frequent landslides, other natural calamities like heavy snowfall, hail storm, etc. The study also not includes the interior designing of the spaces and elements (wall treatments, finishes, flooring, ceiling, etc.)

1.6. Limitations The study will be helpful for architects and designers for proposals of all types of residential buildings but not commercial, industrial, recreational buildings like shopping malls, large office buildings, sports complexes and stadiums. The study includes information about construction techniques and materials employed for particular type of landform but not project management and construction management of execution, materials, time taken for execution, labours and cost.

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The scope of study could be very vast and very much extensive in nature involving all constructional techniques and structural aspects. But, sighting the specific need and the other constraints such as time etc., we should draw a limit to our area of exploration. No live case studies are done because of time constraint.

1.7. Methodology The study encompasses the information on topics from detailed research referring  journals, documents, literature reviews, case studies, in each and every objective of the study. Detailed analysis of the visual character of the local setting, topography, field patterns (using topographical survey techniques), landmarks, historic features and nature conservation interests is done to provide a source of inspiration for the design. Maps and aerial photographs can provide useful indicators of visual character and help to highlight the character of the local landscape or townscape. Topographic survey is done to get the necessary data to produce a topographic map of the earth’s surface. This map will include contour lines, locat ion of natural features, such as streams, gullies, and ditches and man-made features like bridges, culverts, roads, fences, etc. which are needful for detailed planning. The best practical method of presenting topography is by means of contour maps. Analysis of the local landscape and townscape is important to help relate the development more sensitively to its surroundings. Such analysis should include  patterns of landscape and townscape, spatial characteristics and building forms, and the results should be illustrated on plan. The analysis also includes the visual characteristics of building forms and related elements, such as: aspect and orientation; proportion; the balance of solid to void; the shapes and details of roofs, chimneys, windows and doors and the materials used.

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Primary studies about the type of geography of different places in global context from various websites and its response to the building and  building's response to the site

Study about the behavior of building in particula r type of landform through case studies and browsing illustrations of buildings in sloping sites to get the  perspective of spaces

Collection of information about different typologies of residential buildings and their design principles referring various journals and literature reviews

Study of construction techniques, services, circulation patterns, vulnerability assesment, scope of landscaping from various literature reviews,  journals, documents, videos and documentaries

Assimilation of information in proper hierarchy and preparation of report

reviews

Preparation of final report

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CHAPTER-2.

UNDERSTANDING THE TOPOGRAPHY OF

SLOPING LANDFORMS AND DESIGN PRINCIPLES Hillsides are defined as lands in their natural state that have a slope angle of 12% or greater for a minimum horizontal distance of 10 meters. Landforms may be extremely sloped or almost flat. The steepness of slopes can also be described in degrees; however, for the purpose of land development it is defined as either a percent or a ratio. Engineered structural slopes are required in all fill locations where roads, utilities or  buildings are being supported. These slopes can be as steep as 100%, or 1:1, depending on materials used and compaction methods. The use of geotextiles as part of a structurally engineered design can further increase the maximum slope attainable. Typical engineered slopes are 67% or 1.5:1. 1.5:1 slopes, though they may be structurally acceptable, are generally too steep to properly retain the minimum depth of topsoil of 150mm necessary to enable re-growth of native plant species. Minimum finished slopes that will consistently retain topsoil are 50% (2:1) or flatter. (Design Ideas for sloping sites) Sloping sites offer unique opportunities including great views, access to cooling  breezes and often result in more interesting building forms where the design accommodates the slope. They do however require more design consideration than a flat block to balance house design, excavation and potential amenity impacts on neighboring properties. On a sloping site, ‘off the shelf’ designs which have been specifically designed for a flat block should be avoided

to get interested spaces

incorporated in and to achieve greater responsiveness to site. Key importance of slope development is the preservation of land which provides natural space, buffering and habitat for native plants and animals. (Design Ideas for sloping sites)

2.1. Types of sloping landforms There can be diverse types of landforms in sloping sites which are listed below based on the direction and amount of slope which decides the type of spaces in residential  buildings. (Tweed Shire Council)

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2.1.1. Classification based on direction of slope of the site

Landslopes can be classified on the basis of direction of slope as Down slope, Up slope, Side slope and Rolling slope 2.1.1.1.

Up sl ope

1. Site rises up from road. (see Figure 2.1) 2. Generally require more cut allowing for lower level/garage. 3. Garage doors and driveways are generally more visually dominant from the street on up slope lots. A projecting balcony over the garage reduces this visual impact. 4. A level transition off the street level into the elevated living areas should be aim at. 2.1.1.2.

Down slope

1. Site falls away from road. (see Figure 2.1) 2. Garage carports are easier to build closer to the street. 3. An extra storey at the rear should be avoided which significantly increases the  buildings height and bulk from the rear.

Fi gure 2.1: Up slope (left) and Down slope (right) (Tweed Shire Council)

2.1.1.3.

Side slope

1. Site rises/falls away from side boundaries. (see Figure 2.2) 2. House with the garage at lower level with living space above can be designed. 3. Site ‘benching’  and large retaining walls at property boundaries which can lead to overshadowing, overlooking and drainage issued should be avoided.

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2.1.1.4.

Roll i ng sl ope

1. Site rises/falls in two or more directions. (see Figure 2.2) 2. Level change within the building design by splitting the house over different floor levels can be designed. 3. Unsightly retaining walls outside of the building envelope should be avoided.

F igu re 2.2: Side slope (left) and Rolli ng slope (ri ght) (Tweed Shire Council)

2.1.2. Classification based on direction of slope of the site

Landforms may be flat, having moderate slope, steep slope or extreme slope depending upon the terrain which decides the construction techniques to be adopted (whether single slab, post and beam construction or pole construction should be employed) 2.1.2.1.

F lat si tes

Single slab on ground construction are only appropriate up to a slope incline of 4° or 7° as the cut/fill required becomes excessive (over 1.5m). Slopes between 4-6° should accommodate some level change within the building footprint. (see Figure 2.3) 2.1.2.2.

M oder ate slope

On slopes of 6-12°, single slab construction should be avoided (up to 1:5). Two or more slabs or part slab/part post and beam construction techniques should be adopted. (see Figure 2.3 )

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2.1.2.3.

Steep sl ope

On slopes over 12°-18° (1:5-1:3) post and beam construction which steps with the site. This may include a lower part level which may be a concrete slab. (see Figure 2.4) 2.1.2.4.

Ex tr eme sl ope

On slopes over 18° (1:3), suspended or pole construction is required. This degree of slope is more suited to a downslope configuration. Driveway access is generally difficult on upslope lots which require large retaining walls and a curving driveway. ( see Figure 2.4)

Fi gure 2.3: Bui ldin g on flat site (left) and moderate slope (ri ght) (Tweed Shire Council)

F igu re 2.4: Bu il din g on steep slope (left) and extr eme slope (right ) (Tweed Shire Council)

2.2. Buildings on slope: the implications and solutions If a site is flat, the topography may not influence the location and layout of the  building, but on a sloping site, the topography is likely to be a significant design factor. The slope of a site and adjacent surroundings may affect access to sun and views. For example, an east-facing hillside will have reduced afternoon and evening sunlight, particularly in winter, and depending on the height and steepness, a southfacing site may receive little or no sun during the winter months. The position of a new house in undulating and hilly areas needs to be carefully considered to achieve a  practical design which does not look out of place. (Design Ideas for sloping sites)

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2.2.1. Level changes

On a sloping site, a split level floor plan is the most cost effective way to develop a site. However, this will usually involve several small sets of stairs between levels and this can add to costs. Multiple levels may also limit the appeal of a property to households with elderly, disabled, or young members. Changes in level can, however, add considerably to the interest and appeal of the space, for instance, a change in floor level can be used as an informal way of defining different areas within an open plan space, as an alternative to using partition walls which restricts the appeal of the openness of the space. 2.2.2. Upside down living

A sloping site often means that there is a view. One of the best ways of taking advantage of this view is to reverse the accommodation to bring the living areas to the top with the sleeping areas to the lower floors. The garage can be a complicating factor in all of this. If the road is at the higher level, then the solution is for the garage to be designed over the rest of the residential spaces. If the road is at the lower level then there might be no alternative but for it to remain. However, it is likely that in those circumstances the entrance accommodation will also have to share the lower floor. 2.2.3. Building regulations

Building Regulations relating to disabled access can sometimes affect the design of a house on a sloping site. Externally, they require t hat access ramps for slopes up to 1 in 15 should not be longer than 10 meters, and those for gradients up to 1 in 10, no longer than 5 meters. Steeply sloping sites can, in the absence of a ramp, employ steps at least 900mm wide with a rise no greater than 150mm and a distance between landings of no more than 1,800mm. Additionally, if there are more than three risers, handrails must be provided to at least one side. Internally the entrance floor must contain a WC accessible by wheelchair. 2.2.4. Design guidelines for different amount of slopes

All development including grading on natural slopes below fifteen percent (15%) should be designed according to the following guidelines (HRO) :

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1. Building should be oriented with the contours utilizing the natural slopes. (see  Figure 2.5) 2. All development should be sited to avoid potentially hazardous areas and environmentally sensitive areas as identified in the open space as well as to avoid dislocation of any unusual rock. 3. The need for excavation or fill increases complexity of the construction as well as adds on the cost. 4. For steeply sloping sites (e.g. in excess of 1:5) consider suitable split level (stepped) schemes that relate more closely to existing ground levels should be considered. Land should be carefully spaced around the building so that it  blends more successfully with the surroundings while creating further shelter. (see Figure 2.7 ) 5. Excess fill should be either removed or carefully graded around the building to suit the natural slope of the land. 6.  Natural slope should dictate the form. Over excavation and creation of artificial plateau should be avoided. (see Figure 2.6 ) 7.  Natural drainage courses should be preserved, enhanced, and incorporated as an integral part of the project design to the extent possible. Where required, drainage channels should follow the existing drainage patterns to the extent  possible. They should be placed in inconspicuous locations and receive a naturalizing treatment including native rock and landscaping, so that the structure appears as an integral part of the environment. 8. Grading should be limited to the extent possible and designed to retain the shape of the natural landform. Grading must be designed to preserve natural features such as knolls or ridgelines. In no case should the top of a prominent hilltop, knoll, or ridge be graded to create a large building pad; circulation should be aligned to conform to the natural grades as much as possible. (see  Figure 2.5) 9. The use of retaining walls, plantable walls, and terraced retaining structures is encouraged when use of these can eliminate the need for extensive cut or fill slopes. Retaining walls should typically have a height of five (5) feet or less. Plantable walls should be used instead of retaining walls above six (6) feet in 13

height. Terraced retaining structures should be considered when their use can avoid the need for extensive manufactured slopes and retaining walls. (see  Figure 2.5) 10. Slopes steeper than two to one (2:1), appropriately designed by a geotechnical engineer,

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F igu re 2.5: Design pr in cipl es that must be taken care of (HRO)

Fi gure 2.6: Over excavation and cr eation of artif icial plateau should be avoided (North Tipperary County

Council, 2009)

Development including grading on natural slopes between fifteen percent (15%) and twenty-five percent (25%) should be designed according to the following guidelines (HRO): 1. Grading should be utilized only for the construction and installation of roads, utilities, garage 2. Deck construction with excessively high distances between the structure and grade should be avoided. 3. Rear yard should not exceed twenty (20) feet measured parallel to the slope if such yard requires a grading exemption. 4. Single-level residential structures should be oriented such that the greatest horizontal dimension of the structure is parallel with, and not perpendicular to, the natural contour of the land. The slope of the roof should be oriented in the same direction as the natural slope. (see Figure 2.5) Development including grading on natural slopes of thirty-five percent (25%) or over should be designed according to the following guidelines (HRO): 1. Extensive manufactured slopes and retaining walls should be avoided. 2. Landscaping should be utilized to recreate the linear silhouette and to act as a  backdrop for structures. Trees that grow to at least one and a half times the 15

height of the structure should be planted between buildings to eliminate the open gap and blend the rooflines into one continuous silhouette.

Fi gure 2.7: Step buil ding design (Tweed Shire Council)

2.3. Clustering of houses Clustering allows large portions of the original development to be retained in its undisturbed natural state. To ensure that clustering of units does provide the open space desired (City of Vernon- Hillside Guidelines 2008, 2008): 1. Small and larger lot detached housing (reduced yard setbacks); 2. Zero-lot line development (the equivalent of duplexes and townhouses but with each unit owned in fee simple); 3. Multiple family development (e.g., duplex, triplex, etc, townhouse apartment); and 4. Single-family strata development (any of the above where common areas are collectively owned by two or more residents).

16

F igu re 2.8: Standard lar ge lot r esidenti al layout , mixed sin gle fami ly layout with open spaces, mi xed density layout wi th open spaces ( fr om left to ri ght) (City of Vernon- Hillside Guidelines 2008, 2008)

2.4. Scenic opportunities Scenic view opportunities from hillsides are recognized as valuable to both hillside residents and the community as a whole. It is important, however, not to compromise the geotechnical or environmental integrity of the slope to achieve views. View corridors must be identified and strictly maintained for all lots to enable re-vegetation in non-view locations on each lot. Additional criteria include (City of VernonHillside Guidelines 2008, 2008): 1. Buildings should be located to face the view and minimize interference with the views of nearby residences. Buildings should be staggered where appropriate to provide views between units that may otherwise limit the field of view. 2. Buildings should be located so that upslope buildings have views over down slope buildings. If massive grading of the slope is necessary to achieve this concept, it may be necessary to reconfigure the subdivision or layout. The  priority is to avoid disruption of the terrain. 3. Development areas must be sited lower than the ridgeline so that the roof line does not protrude into the ridgeline. Placement of roads, cuts and large or continuous buildings near or over ridgelines should be avoided. Where gaps or interruptions in the ridgeline are unavoidable due to road network requirements, plant trees and vegetation in front of and behind the disturbance to screen and restore a naturally appearing ridgeline. For grassland areas where native trees are limited or nonexistent clusters of viable native trees must be established to provide screening. 4. Development on ridgelines or the top of knolls is not supported and these areas must be integrated as open spaces. Development should be sited and

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designed in a way so as not to alter, disturb or remove significant scenic or environmentally functional features of a parcel.

2.5. Conclusion This chapter concludes that building should positively respond to the site and explore the full potential of site. This chapter also tells about the implications and principles of building design on different amount of slope to avoid the grading as much as  possible.

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CHAPTER-3.

BUILDING TYPOLOGIES, CONSTRUCTION

TECHNIQUES AND SERVICES Most of the sloping landform in India lies in Northern region and North-Eastern region. There large number of construction technologies is employed to suit the terrain. Some buildings are constructed using locally available materials while some are constructed using RCC. Thus there are large numbers of building typologies  prevalent in those regions.

3.1. Residential building typologies prevalent in North India (Assessment Project Group of IIT Bombay, IIT Guwahati, IIT Kharagpur, IIT Madras, IIT Roorkee, 2013) 1. Thathara with timber plank partitions and light weight sloping roof 2. Thathara with Dhajji-Diwari partitions and light weight sloping roof 3. Thathara with infills of stone masonry in mud mortar and light weight sloping roof, dry stone and light weight sloping roof, brick masonry in cement mortar and light weight sloping roof 4. Kath-Kunni walls with stone packing and light weight sloping roof, heavy/stone sloping roof. 5. Mixed Kath-Kunni construction 6. Mixed rammed earth construction 7. Rubble stone (field stone) in mud/lime mortar or without mortar (usually with timber roof) 8. Dressed stone masonry with cement mortar 9. Adobe block walls with sloping roof 10. Unreinforced brick masonry in cement mortar, cement mortar with reinforced concrete floor/roof slabs, mud/lime mortar. 11. Unreinforced concrete block in lime/cement mortar (various floor/roof systems) 12. Masonry mixed structure with reinforced concrete 13. Confined brick/block masonry with concrete posts/tie columns and beams

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14. RC moment resisting frame with unreinforced masonry infill walls (see Figure 3.1), flat slab structure, open ground storey structure (see  Figure 3.1), load  bearing masonry, open intermediate storey structure, mixed infills. 15. RC mixed structure with composite timber, bamboo and others 16. Dry rubble stone masonry with flat slab 17. Mixed dry rubble stone masonry

Fi gure 3.1: RC moment r esisting fr ame with unr einf orced masonry i nf il l wall s (left) and open ground storey stru cture (ri ght) (Assessment Project Group of IIT Bombay, IIT Guwahati, IIT Kharagpur, IIT Madras, IIT

Roorkee, 2013)

3.2. Residential building typologies prevalent in North East India (Assessment Project Group of IIT Bombay, IIT Guwahati, IIT Kharagpur, IIT Madras, IIT Roorkee, 2013) 1. Random rubble stone with mud/lime mortar 2. Dressed stone masonry with cement mortar 3. Mud walls with horizontal wood elements 4. Unreinforced brick masonry in mud/lime mortar, mud mortar with vertical  posts, cement mortar, cement mortar with reinforced concrete floor/roof slabs, 5. Unreinforced brick masonry in cement mortar with lintel bands (various floor/roof systems) 6. Masonry mixed structure with timber, bamboo and other wood elements 7. RC moment resisting frame designed for gravity loads only, seismic features, unreinforced masonry infill walls, flat slab structure, open ground storey structure, composite steel 8. Steel moment resisting frame with brick masonry partitions, light weight  partitions

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3.3. Construction techniques to be adopted while designing the building in sloping sites Design

solutions/construction

techniques

like

step

building

design,

cut/fill

construction techniques, raising the building on stilts/poles, retaining wall construction, drainage issues, seepage problems should be incorporated which respects the site potential upto its full expanse and lessen the impact of landslide and other issues. 3.3.1. Cut and Fill

This describes the process of carving out a level plinth on a sloping site in order to  build a space that is essentially designed for use on a level site. Any spoil that is cut from the bank is reserved in order for it to be brought back to make up the levels on the lower edge. With the cut-and-fill technique, material is removed from the uphill  part of the site and placed on the downhill portion to form a level surface (see Figure 3.2). The fill material may compact and settle later, and cause cracking of foundations and walls. The extra load of a building may trigger a slope failure on unrestrained fill. Retention walls and pre-compaction of fill may lessen the potential for that type of slope failure. (How to Build on a Sloping Site) 3.3.2. Stilts/Poles

Building on stilts is one way of addressing steeply sloped sites (see Figure 3.2). This avoids the need for expensive foundations and also negates the requirement for tanking. The other benefit is that it leaves the ground untouched, allowing planting to take place over much more of the site. It could also be implemented on multiple levels. (How to Build on a Sloping Site)

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Fi gure 3.2: Cut and fil l construction (left) and stil ts construction (r ight) Basements/Retaining walls (Tips for

building on a sloped terrain, 2014) (How to Build on a Sloping Site)

3.3.3. Basement and Retaining wall construction

When creating basements on sloped terrain, the walls are often subject to a lot of force from the surrounding banks of land and therefore becoming retaining walls. Basement construction (see

Figure 3.3)  may have to be strong enough to hold back

considerable banks of ground in which walls behave as retaining walls. In other situations, such as building on a level plinth beside a natural or carved out bank, it may be necessary to construct separate retaining walls. In certain circumstances it may be cheaper, and visually more attractive, to construct a series of lower retaining walls with the ground stepped between them. Structural engineers should be consulted to be involved in the design of these structures, and detail design stage is important to ensure good water proofing. Another option is stepping the ground by using low level retaining walls, or gabion walls which are wire cages filled with stone or interlocking concrete blocks that are subsequently filled with soil. (see Figure 3.4) Retaining structures are relatively expensive but necessary in steep areas to gain roadway space or to support the roadbed on a steep slope, rather than make a large cut into the hillside. They can also be used for slope stabilization.  Figure 3.5  presents information on common types of retaining walls and simple design criteria for rock walls (see Figure 3.7 ) where the base width is commonly 0.7 times the wall height. Different construction principles are employed for retaining walls of different heights. (see  Figure 3.6 ).  Figure 3.5 and  Figure 3.4 shows the Gabion structures which are commonly used for walls up to 5 meters high, particularly because they use locally available rock and are labor intensive. These are commonly used for low gravity retaining structure because they use locally available rock and are relatively 22

inexpensive. (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS) The use of retaining walls is not encouraged. These are only supported where they  preserve native undisturbed areas, address unstable native slopes or rock faces, or form part of the neighborhood character. Where provided, the following criteria should be considered in their design (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS): 1. Retaining walls should respect the natural character of the site and not present a large uniform wall face that overpowers the site and disrupts animal movements. 2. Retaining wall height should not exceed 3.0 m for roads and site specific works, 1.2 m for yards. Higher walls may be appropriate where they are articulated, have a surface texture/pattern, or where sufficient landscaping is  provided to screen the wall. 3. Smaller stepped retaining walls are employed instead of a large uniform wall. The height and depth of the wall steps should be consistent with the natural terrain or with the slope above and below the walls. For stepped retaining wall systems, the walls must be designed to permit landscaping of the terraces that will screen the wall, including irrigation to all terraces. Landscaping of the terraces using mixed hardy native shrubs or trees is required. Width of each terrace proposed must be sufficient to enable the landscaping required and  permit access for maintenance. 4. Retaining walls must be set back from utilities and the traveled portion of roads to enable planting of screening landscaping.

F igu re 3.3: Basement constructi on on slopin g sites (Tips for building on a sloped terrain, 2014 )

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Fi gure 3.4: Typical r etaini ng wall constru ction, Gabion wall and rock buttress (from left to ri ght) (Slope

Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BM PS)

Fi gure 3.5: Common types of r etaini ng structur es (Slope Stabilization and Stability of Cuts and Fills- LOW-

VOLUME ROADS BMPS)

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Fi gure 3.6: Constru ction detail f or r etaini ng wall of height upto 2 m (left) and 5 m (right) (Slope Stabilization

and Stability of Cuts and Fills- LOW-VOLUME ROADS BM PS)

Figure 3.7: Typical rock wall construction for smooth backfill (left) and face with steps (right) (Slope

Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BM PS)

3.3.4. Storm water management and Drainage system

Implement methods for collection, conveyance, control and treatment of storm water is employed that mitigates potential impacts and emulates the area’s natural water cycle. This is required to limit runoff from new development based on the soil capacity and sensitivity for ground recharge. Having a sloping site may involve extra costs with drainage and. If site slopes down from a road in which the sewer is fairly shallow then, pumped sewage system can be used. But if the sewer is quite deep, then the slope may actually represent a saving in cost, as the resulting house drainage will not have to be as deep. Sloping down from the road means that surface water can collect around the base of the lower floor. This may mean having to install a drainage channel to divert the water to soak ways.

25

Sloping up from the road may at first seem the best option, but many local authorities will not allow surface water to go into the public sewers and many require that  precautions are taken to ensure that surface water does not flow onto the road. (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS)

3.4. Roads: Road designs are typically site specific and may require input from geotechnical engineers and engineering geologists. Slope failures, or landslides, typically occur where a slope is over-steep, where fill material is not compacted, or where cuts in natural soils encounter groundwater or zones of weak material. Good road location can often avoid landslide areas and reduce slope failures. When failures do occur, the slide area should be stabilized by removing the slide material, flattening the slope, adding drainage, or using stabilizing structures. Failures near streams and channel crossings have an added risk of impact to water quality. Certain points to be taken care of while designing road on sloping sites (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS): 1. Grading for the construction of access roads or drainage ways shall be minimized so that the visual impacts associated with said construction are mitigated to the greatest extent possible; 2. The construction of access roadways or driveways should be accompanied by sufficient berming and landscaping/erosion control so that visual impacts associated with said construction are promptly mitigated. 3. If the city engineer determines that no hazard to pedestrian or vehicular traffic will be created, a garage or carport may be built to within five (5) feet of the street right-of-way line. 3.4.1. Classification of access routes

Depending upon the terrain conditions, access routes may be classified as: (California Coastal Commission) 3.4.1.1.

Two- L ane Access Road

(see Figure 3.8) 1. Ingress and egress provided by 1 road. 26

2. Merges easily with existing access and conventional roadway designs. 3. 9' minimum width for each lane, required for fire saf ety. 4. On steep slopes, disturbed area for cut and fill will extend far beyond limits of road bed and shoulders. 5. Careful drainage controls needed along road and modified slopes. 6. Broad road area may be visible from great distances. 7. Additional road may be required for emergency access. 3.4.1.2.

Spli t L evel Access Road

(see Figure 3.8) 1. Ingress and egress provided by 2 roads. 2. 9' minimum width for each lane, required for fire saf ety. 3. Split roads can be "stacked" to minimize visual impact, cut and fill can be reduced. 4. Careful drainage controls needed along road and modified slopes. 5. Separate roads may provide emergency back-up when secondary access is required.

F igu re 3.8: Two lan e road (left ) and spli t level access road (r igh t) (California Coastal Commission)

3.4.1.3.

Sin gle Lane with Pull outs

(see Figure 3.9) 1. One road providing ingress and egress. 2. Minimum width for lane should be 10' with turnouts, required for fire safety. 3. Land form alteration for cut and fill can be minimi zed. 4. Periodic road widening needed for pull-outs and turn-around. 27

5.  Not suitable for high-density vehicle use. 6. May require secondary, back-up road for emergency situations. 3.4.1.4.

Bridge

(see Figure 3.9) 1. Can span stream bed and most riparian habitat, if stream is narrow. 2. Most appropriate for high-use roads which cross perennial streams. 3. Structures can be expensive, need to assure sufficient width, turning angle and height for emergency vehicles. 4. If bridge can be built without supports in stream, can avoid impacts to flow and habitat. 5. Design must consider high flood events 6. A large bridge structure may dominate visual character of area.

Fi gure 3.9: Single lane road with pull outs (left) and bri dge (ri ght) (California Coastal Commission)

3.4.1.5.

Cul ver t under Road

(see Figure 3.10) 1. Stream flow is channeled into a culvert and roadbed is constructed on top. 2. Only suitable for intermittent or low-flow streams or as part of area-wide drainage plan for directing surface flow. 3. Road could provide primary access. 4. For stream crossings, a culvert will disturb banks.

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3.4.1.6.

Ar izona Cr ossin g/For d

(see Figure 3.10) 1. Roadbed built directly into stream bed. 2. Stream bank and habitat at crossing will be disturbed by road. 3. Road should be a low volume road or secondary access. 4. If used for primary access, a secondary access should be provided for flash flood events. 5. Due to low-profile, fords rarely alter visual character.

 (California Coastal Commission) Fi gure 3.10: Cul vert (l eft) and Ar izona crossing (r ight) 

Design criteria that should be considered while planning for sidewalks include (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS): 1. Sidewalks must be set back from the road a minimum of 1.5 m to accommodate snow storage (for cold regions). 2. Sidewalks are to be located on the same side of the road due to the winding nature of hillside roads. The location for sidewalks must be set to maximize the function as a safe pedestrian corridor through the development and provide scenic views where possible. 3. Sidewalks on both sides of the road may be required for short distances to  provide walking linkage between roads and to provide improved sight distances for road crossings. 4. The requirement for sidewalks on local cul-de-sac roads may be waived where low traffic volume is generated, provided alternate off street pedestrian facilities exist. 5. Curvilinear or meandering sidewalks and pathways may be used where they eliminate long sustained grades. Varying offsets between the road and the

29

sidewalk may also be considered where it will save a significant feature or reduce grading requirements. 3.4.2. Cut slope design options

In this technique, earth is cut from one pat and filled to other part to make access route. For most of the hillside construction (slope between 0-60 percent), balanced cut and fill (see Figure 3.11) is adopted because it can be done for most of the soil types. In case of rocky terrains, a full bench cut (see  Figure 3.12) is adopted for slope more than 60 percent and through cut is adopted for slope between 0-60 percent. (see  Figure 3.13) (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS)

Fi gure 3.11: B alanced cut and fi ll for most of th e construction on hi ll slopes (Slope Stabilization and Stability

of Cuts and Fills- LOW-VOLUME ROADS BMPS)

F igu re 3.12: F ul l bench cuts for slopes exceedin g 60% (Slope Stabilization and Stability of Cuts and Fills-

LOW-VOLUME ROADS BMPS)

30

Fi gure 3.13: Through cut (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS

BMPS)

3.4.3. Fill slope design options

Fill slope design solutions include typical fill (see  Figure 3.14), benched slope fill (see  Figure 3.15), reinforced fill (see  Figure 3.16 ), through fill (see  Figure 3.17 ). (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS)

Fi gure 3.14: Typical fil l (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS

BMPS)

Fi gure 3.15: Benched slope fil l wi th l ayer placement (Slope Stabilization and Stability of Cuts and Fills-

LOW-VOLUME ROADS BMPS)

31

Fi gure 3.16: Reinforced fil l. T hese can be used as an alternative for r etaini ng wall (Slope Stabilization and

Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS)

Fi gure 3.17: Through fill (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS

BMPS)

3.5. Practical considerations (landslide or slope stability) The steepness does not necessarily correlate with the stability of slopes. Slope stability depends on factors such as geologic materials, soils, moisture content and vegetation cover. A comprehensive geotechnical investigation is required for developments on slopes to provide the detailed information necessary to ensure slope stability. Various studies have found that soil slips, which cause avalanche failures, commonly initiate on slopes greater than 33%; slower moving earth flows occur most often on slopes 30% to 60%. Nevertheless, serious erosion can occur on much shallower slopes and the potential for erosion is greatest in the period between removal or disturbance of vegetation and re-establishment of new vegetation. Decisions on suitable methods for slope stabilization first require an evaluation of the hazard. Deep mass movements (deep landslides) are difficult to control and require engineering solutions. Shallower mass movement (shallow landslides) and erosion  processes are more suitable for control using bioengineering or eco engineering. Bioengineering techniques combine engineering methods with natural or living materials to protect or restore slopes and reduce erosion like using brush matteresing, and the planting of shrubs, plants and trees to stabilize the soil. 32

Methods include the use of stone, steel, concrete and geosynthetics to stabilize or shore up slopes that are liable to landslides. These methods should, where possible, be combined with use of plants and trees to enhance the urban green space. (California Coastal Commission) There are various construction techniques by which landslide stability can be achieved on slopes (California Coastal Commission): 3.5.1. Conventional Buttress Fill Slope

1. Extensive grading is required for steep slopes, since fill must be designed at 2:1 or 1.5:1 (horizontal to vertical). 2. Extensive surface disturbance and loss of habitat from fill area. 3. Finished slope does not blend with natural terrain min steep slope areas can be varied to blend with natural terrain. 4. Surface and subsurface water flows must be controlled as long as fill slope exists. 5. Drainage must be maintained; water cannot be directed to a modified slope. 3.5.2. Contour Graded Slope

(see Figure 3.18) 1. Extensive grading required if natural slope is steep; slope must conform to local grading standards. 2. Some disturbance of surface area and habitat. 3. Finished slope can be varied to blend with natural terrain. 4. Surface and subsurface flows need to be controlled, as long as slope exists. 5. Portions of natural vegetation can be maintained. 3.5.3. Steep Geogrid Slope

(see Figure 3.18) 1. Slope can be constructed with little grading, even in steep terrain. 2. Finished slope can be steeper than a conventional buttress fil l, up to 1:1. 3. Surface and subsurface flows need to be controlled as long as slope exists. 4. Can be constructed where space is limited. 5. Finished slope can be varied to blend with natural terrain. 33

3.5.4. High Retaining Wall

1. Can be constructed with very little grading. 2. Structures can be expensive, need to be carefull y designed and constructed. 3. Drainage behind wall must be controlled as long as wall exists. 4. Useful for areas with limited construction space. 5. Rarely blends with natural terrain; surface treatments are possible. 6. Can be used for some landslide remediation. 3.5.5. Several Low Retaining Walls

1. Can be constructed with very little grading. 2. Only suitable for small slope instabilities, or for small cuts or fills. 3. Drainage behind walls needs to be controlled, as long as walls e xist. 4. Small walls can be camouflaged be vegetation and often can blend into natural terrain. 3.5.6. Gravity Wall/Crib Wall

1. Walls require more disturbance than retaining walls, but less than a buttress. 2. Since structure is open, surface and subsurface flows can go through the structure; little drainage control needed. 3. Can be used for some landslide remediation. 4. Facing will not blend with natural terrain; some planting between the facing elements may be possible.

F igu re 3.18: Contour graded slope (left) and Steep geogri d slope (righ t) (California Coastal Commission)

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3.6. Recommended practices (Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS BMPS) 1. On steep ground (>60% slope) full bench construction should be adopted. A narrow, single lane road with turnouts is constructed to minimize excavation  but road should not be much narrow so that it causes accidents 2. Cut slopes should be constructed in most of the soils using a cut slope ratio of 3/4:1 to 1:1 (horizontal: vertical). Flatter cut slopes should be constructed in coarse granular and unconsolidated soils, in wet areas, and in soft or clay-rich soils. Cut slopes in rock should have a ratio of 1/4:1 to 1/2:1. 3. Vertical cuts (1/4:1 or steeper) should be adopted only in stable rock or in very well cemented soils, such as cemented volcanic ash or in-place decomposed granite soil, where the risk of surface erosion is great and the risk of local failures in the steep cut is low. 4. Unsuitable or excess excavation material should be disposed in locations that will not cause water quality degradation or other resource damage. 5. Fill slopes should be compacted well in sensitive areas or when the fill is constructed with erosive or weak soils to avoid la ndslides. 6. Retaining structures should be placed only upon good foundation materials, such as bedrock or firm, in-place soils

3.7. Conclusion This chapter tells about the residential building typologies prevalent in Northern and  North Eastern region of India and construction techniques to be adopted while designing the building on sloping sites. This section focuses on cut/fill construction techniques, construction of building on stilts, retaining wall construction, rock wall construction, etc. Road design criteria are also discussed focusing on cut/fill slope design options. Landslide or slope stability is also taken into consideration.

35

CHAPTER-4.

LANDSCAPING ON SLOPING LANDFORMS

Slopes offer a great challenge than flat ground when it comes to landscaping. The  biggest concern is usually the risk of erosion. Additionally, planting and maintaining  plants on inclines can be a difficult undertaking and take a little more thought and effort than for a normal 'flat' garden but the results can be very unusual - and a much more interesting garden can be created. If slopes are very steep or complicated, landscape architect must be preferred, who can advise on this aspect of your garden design, and make sure the design and the works are structurally safe and sound.

4.1. Planning a landscape on slope Planning a garden with slopes will surely be a challenge, but changes of level certainly give any garden added interest, and add an extra aspect to sloping landform design. Sloping garden designs will need to be very carefully thought about at the  planning a garden stage. Designing a garden on sloping landform will depend on: 1. The severity of the slope (degree of slope or steepness of slope) 2. The size of the garden 3. Features to be included Factors to be considered while planning a landscape on slope (Anderson) : 4.1.1. Drainage

If water drains to the down of the slope, water channel clues and channels are narrow, then the erosion control will be a problem and slope may be more unstable than required. This is something to keep in mind when landscaping is done  –   slope stability. To check this, a hole is dug and filled with water and time taken by water to drain is noted. If drainage occurs within an hour or so, slope is relatively stable. If it takes several days to drain, then slope is highly unstable. Water accumulation on the slope is controlled because wet soil and mud on a steep hill can cause erosion and slide issues.

36

4.1.2. Soil

Proper analysis of type of soil and is water holding capacity should be done. It will decide the type of planting material that will best grow here and better secure the slope. To check the type of soil, a hole should be dug somewhere on the slope,  preferably where landscaping is to be done and result is noted down. If soils on top slides down the slope easier, then the soil is rocky or clayey. (Anderson) 4.1.3. Access and maintenance

Access to gardens on slope is necessary for maintenance, weeding, pruning and watering, and can take different forms. If a very small garden, access can be made from the edges. Larger gardens require access via paths, walkways or steps. Steps and  paths down the slope can be used to more appropriately access the terraced gardens. (Anderson) 4.1.4. Rainwater and runoff management

Rainwater and runoff management is interrelated with irrigation, plant selection and erosion control. Rainwater can prove harmful for a hillside garden. If unchecked, it can cause serious erosion. Rain running down the hill and off the landscaped area into the residential spaces is a problem. Rain can become an asset with proper design. Terraces accomplish this inherently by providing level garden areas for the rain to soak in and not runoff. Where a slope is not terraced, berms across the hillside with narrow swales behind, and winding stone-lined creek beds can slow the movement of water, allowing it to soak in. Garden at the bottom of the slope allows the last of the runoff to gather and irrigate plants assembled there. If there is a slope uphill from the residence, berms can also be used there to send surface water around the house for use in lower gardens. Aesthetically pleasing ground cover is also an easy solution to control water runoff. If the slope is not too steep, a ground cover creates a clean appearance that is easy to maintain. Ground covers such as Blue Rug Juniper, Baltic English Ivy and buffalo grass are low maintenance and well suited to sloped areas. There are also flowering ground covers for inclines like Creeping Phlox, Vinca Minor vines and Sweet Woodruff. (Anderson)

37

Boulders or rocks should be strategically placed around the plants to slow down any water runoff. Stones offer a natural appearance, but they also trap the earth and moisture within it. 4.1.5. Irrigation

Since hand watering of a landscaped area on slopes is not very convenient, there is a need to install drip irrigation. Alternatively, on a low-water slope landscape, drought tolerant plants can be selected; hand watering them first two summers can be done, rather than installing irrigation. Plants put at the top of a slope will get the least water, those in the middle somewhat more, and those near the bottom the most, as water running downhill section is soaking in more and more. Accordingly; top, middle and bottom regions are planned. The most drought tolerant should go toward the top, and those that can tolerate more water closer to the bottom. Exposure plays a factor too. And the direction the slope faces will impact plant selection; southern and western exposures are hotter, and northern and eastern can take plants that can stand less direct sun. (Anderson) In addition to normal gardening issues mentioned above, particular challenges hillside gardening must also be considered while planning a landscape on sloping site: 1. Erosion control and retaining the hillside 2. Rainwater and Runoff 3. Structural safety for landscape design 4. Plant selection and location — for erosion control and relating to water needs and exposure 5. Zoning and water behavior on slopes 6. Accessibility to the beds or plantings for maintenance and moving 7. Steepness of paths and steps, and safety aspects Design considerations for gardens sloping up away from the house (or sloping down towards the house)

A garden that slopes up from the home is one that can be seen to an even greater degree than a flat site. It becomes a garden that can be terraced so as to bring aesthetical values to the residence.

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1. Patio on a higher part of the garden, away from the house may look interesting. Raised wooden decks can be attractive and they can be constructed in such a way as to allow light to filter down to the windows of lower storeys. 2. The rest of the garden could be a series of attractive terraces probably with steps. 3. Professional advice on structure should be taken and as to avoid water running down the slope and collecting near the house. (Sloping Garden Design Ideas, 2014) Design considerations for gardens sloping down away from the house (or sloping up towards the house)

1. High level decking may look interesting. 2. The rest of the garden could be terraced with steps, and attractive planting and groundcover to make space look aesthetically pleasing. 3. Advantage of great views. (Sloping Garden Design Ideas, 2014)

4.2. Landscaping principles on sloping sites Hillside landscaping is the most challenging of all residential design problems. Whether it is a natural undisturbed slope or one composed of cut-and-fill, there are five essential principles that should be taken care of while designing on slopes. (Gilmer) 1. Views should be preserved while solving problems.

Residence built within forested hillsides often cleared to increase the view. The trees have vast roots that have held the soil in place for a long time, and when trees are cut down the roots die and the soil becomes vulnerable. For this reason it is far better to keep trees living whenever possible. All the new trees, shrubs and structures proposed between the house and top of slope should be taken care of. If trees are too large these can interfere with the view. Trees planted on the slope itself can over time exceed the height of the slope to encroach into the view. This is more important where a terrace may be graded into the slope further down where trees are planted for shade. Trees with a low spreading

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canopy should be planted rather than an upright conical form such as a fir tree to avoid repeated topping in the future. (Gilmer) 2. Slopes should be taken up gradually as possible.

A very gentle slope is not much different than a ‘flats’ garden, but a steeper slope certainly is. Any time a slope is cut its integrity is compromised, therefore its more better if less slope is cut. Cutting into a slope removes topsoil to expose subsoil, often heavy clays or shale that are poorly drained or lack microbial action of a living topsoil. This is why the planting on so many cut slopes and home pads on exposed subsoil are prone to failure. To preserve the slope, grading is done with a series of shorter terraces rather than one or two very large ones graded with cut and fill. The larger terraces may require extreme erosion control measures on the cut slope and a substantial retaining wall must be specially engineered to hold the fill. Such walls are constructed with footings, sometimes extending down to bedrock. Residences on moderate to extreme slopes are  prone to mudslides and slope failures in extreme weather. (Gilmer) 3. Plants with extensive root system should be used to bind the slope deep underground.

Erosion and depth of the soil can be issues in a sloping garden, so choosing the right  plant for the right spot is the key. Slope is composed of different soil la yers. When the slope has been altered to create building pads, the natural binding of layers may be lost or compromised. When extreme weather such as heavy rains falls on these sites the water may travel through weaker seams to saturate layers deeper down. When they become wet enough they lose their cohesive qualities and slough off in layers. This is usually the cause of slope failures during rainy seasons. When planting is done on slope, trees are selected with a deep network of fine roots. The larger the root system the better, so trees are highly effective at binding subsoil layers, with their extensive roots. There has been a great deal of study on the use of fast growing drought resistant trees such as acacia, planted on slopes. They were topped every year or two to force growth energy into expanding the roots for more effective soil binding. Thought effective, the maintenance required by this technique 40

 precluded widespread use, but it is still recommended as a powerful tool for solving site specific problems. (Gilmer) What to plant on a sloping landform and where on the slope to plant various species are key considerations. Shrubs require less maintenance than perennials, and in addition, generally have a more extensive root system. Attractive foliage or flowers can be chosen, and mix and matched to create attractive mounds of color and texture. Plants like geraniums and begonias can be planted to protect slopes from being washed away by rain. Good plants for a slope also include California lilac, Creeping  juniper, Purple coneflower, Rattlesnake master, Russian sage, Snowberry, Star  jasmine, common periwinkle, Siberian carpet cypress. c ypress. Add plants that strengthen and  bind the soil while adorning the slope. (Anderson) Shrubs which can be planted on slopes include Arctostaphylos, Ceanothus, Erica, Helianthemum and Euonymous. Drought tolerant plant selections include Baccharis  pilularis 'Twin Peaks', Cistus, Correa, Grevillea, Mahonia, Rhamnus and Rosmarinus. Ground cover plants are a perfect solution for covering sloping areas. Using ground cover plants on any slope helps retain or hold the soil on the slope. Additionally, groundcovers fill the area and crowd out weeds, making it easier to maintain. Hardy  perennials and shrubs can also be included as groundcover plants like hostas, sage and snowberry. Ground cover plants such as Aubrietia are excellent for steep banks; they suppress weeds, help stabilize the soil and needs low maintenance. (See Figure (See  Figure 4.1) 4.1) Planting pockets near the large boulders should be created for seasonal color or creeping shrubbery like Cotoneaster or vinca. The stones can be treated with the moss and to give them a weathered and time-elapsed effect. A small stream can also be put in with for sound and visual effect. While putting larger trees on slopes, certain things should be taken care of. Area where the trees are to be planted should be leveled off so the tree stands on level and not on a slope. A retaining wall can be put behind the tree to prevent dirt from washing over the roots too much. Decorative stones can also be used to turn it into a focal point. Too many upright plants should be avoided because they block the view. Larger trees, shrubs and plants should be planted vertically, not pointing out of the hillside. A small half well wel l on the bottom side of the plant should be built to help retain

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water and allow it to soak into the soil around the plant. Smaller plants and ground covers can be planted to fill in while larger plants take hold with the hillside. Composting the soil usually proves helpful —  helpful — certainly certainly if hillside soil is sandy or clay. Hillside gardens, like all gardens should be well mulched. But the choice of mulch is more critical. Things like straw, small bark or cocoa hulls will wash away easily. Finely shredded redwood, or the coarser shredded rather than chipped mulches tend to knit together into a mass, and are less (but not completely) susceptible to being  pushed downhill by rain. (Anderson)

F igu re 4.1: Gr ound covers for steep steep slopes slopes (Alders)

Certain points should be taken care of regarding landscaping on slopes: 1. Retain all trees, hedgerows and other existing features (e.g. streams, rock outcrops) to provide a framework for the garden. Create new hedgerows of mixed native species 2. Avoid large expanses of manicured lawns and suburban style gardens with exotic species, these usually appear alien to their surroundings and do not  provide habitats for wildlife. 3. Plant the space between the house and the front boundary with trees in informal clumps. 4. Trees and shrubs which are locally native will be easier to establish than more exotic species, and in keeping with the character of the area. 5. On exposed sites, consider more substantial shelter planting of native trees to help reduce the effects of cold winds and driving rain, whilst also increasing  privacy.

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4. Surface soils should be protected from rain spatter and runoff.

When rain falls on the slope, each drop that falls on bare earth dislodges particles of soil. As runoff runs down slope, the velocity causes more particles to be scoured from the surface of the soil. This is the basic cause of erosion. Anything that slows the speed of runoff such as rocks or plants reduces scouring and protects the soil. Slopes are planted to cover soil and to slow the runoff velocity. Freeway slope planting is the most widespread example of how a single monoculture of spreading plants such as ice plant or African daisy is used to protect the surface. Although it solved the problems of scouring and slowed velocity, there was nothing to  prevent sloughing. (Gilmer) 5. Ways for maintenance and accessibility should be planned.

When planning any kind of landscaping on a slope, it is vital to allow for maintenance access. An open through-way should be provided to drag cut material out of the area and into trucks. These accessibility paths need not be paved, just fairly level and open. Both vertical and horizontal access across the slope should be planned. For a large site, access might be made easier by designing a gently curving flight of steps. They should be wide enough to allow two people to pass one another. The grade of the sidewalk corridor is often determined by the grade of the street. Whenever possible, however, the grade of the sidewalk corridor should not exceed 5.0  percent. Additional effort is required for mobility on steep grades. Manual wheelchair users may travel very rapidly on downhill pathways, but will be significantly slower on uphill segments. Steep running grades can be better tolerated by providing level segments at intervals. In addition, less severe grades that extend over longer distances may not tire users as much as shorter, steeper grades. (see  Figure 4.2)  (Federal Highway Administration, Updated: 02/10/2014)

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F igu re 4.2: Steep sidewalk gr ades are a sign if icant bar ri er to access for many pedestr ian s (left), I f h e side walk grade exceeds 5% level landings should be provide at regular intervals (right) (Federal Highway

Administration, Updated: 02/10/2014)

4.3. Ways of landscaping a sloping site Depending on size of the slope, hillsides can be divided into more manageable sections with retaining walls which are strong and stable barrier walls usually made of stone, concrete or lumber. These walls can be placed where they will hold back the soil above, and make a space below that can be left as a slope, leveled, or planted. Multiple walls can be placed at different points to create a terraced look. Terraces can range from a few feet wide and used as planting areas to wide expanses. If the slope is more vast, landscape experts recommends putting an 8-10-foot terrace every fifty feet to make the slope much more functional long term. (Anderson) 4.3.1. Terracing

Terracing has historically been the best way to deal with slopes, which can be difficult and even dangerous to maintain. A terraced landscape is created by building a series of retaining walls if the incline is too steep to landscape, allowing space for level beds or lawns. Terracing not only creates a gradual transition to the lower level, it provides  beds for planting. Terraces also help to create flat areas for planting, also patios or  ponds. The steeper the slope, the better the garden will behave if terraced. Terracing is attractive, and also helps prevent runoff and allows rainfall to seep into the soil. And the steeper the slope, the closer together the terraces will be. Methods of creating and holding terraces include stonewalls, wood frames, like a larger version of half a raised  bed, concrete retaining walls, and several other methods.

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From stone and brick for traditional gardens to concrete, metal and railroad ties for contemporary landscape designs, there is wide choice of materials to create retaining walls, but the plantings are what can really add style to the terrace. The appearance of the retaining wall can be softened by adding ground cover and plants that spill over, such as tumbling phlox. (see Figure 4.3) There are many points to consider when planting terraced beds: the materials used for the retaining walls, the right plants for the conditions created and the balance of the  plantings in relation to the hardscaping. By considering right approach, not only hardscaping can be prevented from becoming too dominating or intrusive but the aesthetical benefits can also be enjoyed. (Anderson)

Fi gure 4.3: Gardens showing terracing (Washburn)

4.3.2. Tiering

Creating tiers down the slope make it less likely to erode. By digging into the hill at certain points, tiers can be created for planting. Walls of the tiers can be retained with stone pavers and different plants and landscaping elements are layered to create contrast between tiers. If rock walls are used as tiers; plants, small trees, or even river rocks can be used for a natural look. 2-inch-deep trenches along the borders of the bottom and two sides of each tier should  be created. The trenches should be wide enough for the blocks, stones or posts that are chosen for the wall. Then the material should be for the wall in the trenches. The height should match the high ground that makes up the top border of each tier. (see  Figure 4.4) Each garden bed should be filled with a mixture of half organic compost and half  bagged garden soil to give the garden a deep, rich and loose growing foundation. (Anderson) 45

 (Alpha Landscapes Design ltd.) Fi gure 4.4: Construction of tiered garden 

4.3.3. Changes in levels

Change in levels can be as little as a single step up or a more dramatic sloping garden design, with a retaining wall and steps. Steps add interest to the landscaped space. Even a whole series of terraces can also be created. Small (or larger) areas for patio and small planting pockets can be carved out of slopes to put the plants, shrubs and trees. If the slope is not dangerously steep, incline can be enhanced with paths or staircases made of stone. But if the slope is very steep, a winding path can be designed made of  pavers or bricks. (Anderson) 4.3.4. Rock Landscaping

Rock gardens add natural charm to the space while also holding plants and soil in  place. If they are done well, they can look most impressive. Hills and slopes can be enhanced by means of adding some rocks to create planting pockets and ledges, and an attractive rockery garden can be created. Indentations should be created where rocks can sit without rolling and different-sized rocks of varying texture and color should be placed together in groups. To avoid a complete rock look, spaces should be left between groupings and medium-height  plants or flowers are added. When designing a rock garden, large and small stones 46

should be randomly mixed together, filling gaps in with mulch and plants. Alpine  plants and grasses, should be planted among the rocks to give the illusion they are  placed by nature. (See Figure 4.5) To blend the steps into the layers of a rock garden, two or more steps may be made to merge into one layer, by ‘bending’ the steps round towards the layer. This is the only time in a rock garden that one layer of stone may be mounted on top of another successfully and with a pleasing effect, provided that not too much of the first stone is obscured. (Anderson) Climbers and wall shrubs can be planted to lessen the stark effect of the walls but as they create the problem of leaf fall, evergreens or even the smaller shrubs and climbers are better. Alpine plants can be best option to fill the rock landscaping as they are very well suited to rocky terrain. The factors governing the design of a sloping rock garden are the same as for the flat site. Informality can be best maintained by keeping any steps away from extreme ends and middle ground. Each layer should be given a keystone which should form the highest point for, unlike a flat site, the strata will fall gently to each side, as well as leaning back sufficiently to keep stability. Therefore, the stone will generally get shorter towards the end of the site, or else a gap will appear between the base of the upper and the lower layer. There are no rules governing the steepness of steps but it is obviously easier if they are not too steep and a good guide is to make about two and a half times more tread than riser height. The steepness of slope will determine the rate of rise of stone to be laid. The greater the rise, the closer the layers of stones will be and vice versa. (Rock Landscaping Ideas –  Flat and Sloping Sites)

Fi gure 4.5: Rock landscaping (DI Y network)

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A path though the rock landscape should be wide enough to allow two people to pass one another. Gently curved paths are more effective than angular or sharp-cornered ones. At the lowest points on the site, silt traps covered with channel grating should  be constructed. Drainage tiles should be laid at lowest point in the garden. Another alternative to leaving the path bare is to pave it using the same type of stone as for the rock garden. The stones should never be shallower than 7cm (3 inches) unless they are bedded on a cement base. (Rock Landscaping Ideas –  Flat and Sloping Sites)

ke stone F igu re 4.6: A slopi ng site, made up of semi cir cular layers. The key stone is the l argest stone. Subsequent stones get pr ogressively shall ower so that th ey disappear in to th e ground at th e sides of the site. (Rock Landscaping

Ideas  –  Flat and Sloping Sites)

4.4. Erosion control for residential hillsides Hillside retention and erosion control are two key issues in slope landscaping. There are two factors, which are partly driven by aesthetics, partly by cost considerations and influenced by steepness. If slope is left natural, plant selection is doubly important. Shallow-rooted plants on a hillside are of less importance on slopes than deeply rooted plants. They help to retain the hill and avoid erosion. Perennials that have deep root systems and well-rooted grasses and small and medium shrubs  perform this function well. Erosion has always been a problem for hillside. Each slope demands a slightly different approach to erosion control techniques. Cut slopes are more prone to surface erosion problems. Fill slopes experience surface erosion too, but are also prone to subsurface problems that result from incomplete compaction prior to construction. Worst case is so much underground moisture contributes to liquefaction that destabilizes the earth.

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How the slopes are treated matters because there's always potential for erosion. Every raindrop that falls on bare soil dislodges soil particles. As it gathers and runs down the slope, more soil particles are picked up. Every particle lost in the water has to go somewhere. They will settle out when the runoff slows, and in these spots silt builds up. It is a huge problem when silt deposits interfere with driveway stability of other structures. It becomes a community issue when it clogs neighborhood drainage structures and storm drains. (Gilmer, Landscaping Network) 4.4.1. Factors responsible for Erosion Control

There are many factors which are responsible for erosion control out of which angle of repose and soil types are most important: 4.4.1.1.

An gle of r epose

The angle of repose of a soil is the gradient of the slope at which the soil settles naturally. A firm soil will have a steeper angle of repose than a loose soil. The angle of repose can range from 0° to 90°. Smooth, rounded sand grains cannot be piled as steeply as can rough, interlocking sands. The steeper the slope, the faster water runs off, which creates challenges getting enough moisture to every plant. 2:1 - This is the steepest incline capable of supporting plants. Sometimes these slopes will require retaining walls due to the great amount of siltation they produce. 3:1 - This is the steepest incline allowed for a lawn due to the limitations of lawn mowers. 4:1 - This is a more ideal slope which can be easily planted, and irrigation water is more likely to soak in. 4.4.1.2.

Soil T ype

Most fill slopes have no difficulty with soil types, but on cut slopes it can be a real challenge. This not only influences how much time it takes to dig a planting hole or trench for irrigation, it greatly affects the speed at which water penetrates the ground. Low fertility makes it tough for young plants to become established. Very dense soil resists moisture absorption unless it is applied at a very slow rate. Irregular soils with veins of stone or bedrock may limit the digging of planting holes. Fragmented soils

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fail to hold together once disturbed, leading to future erosion problems, particularly in sandstone and shale. (Gilmer, Landscaping Network) 4.4.2. How Plants Control Erosion

Plants are natural protectors of soil. They cloak the ground in foliage which prevents rain drops from falling directly onto soil particles. Instead, the plants diffuse the energy of raindrops so they filter down to the soil surface more gently. Plant roots help to bind soils underground. Those species with a large proportion of fine roots that spread over a large area prove the best choices for slope stabilization. The nature of how a plant roots as well as its growth habit dictate its value as erosion control plants. The planting should be a mix of groundcover, shrubs, trees, and perennials with the areas between plants covered with mulch or boulders. A mix of plants and vegetation layers ensure that when it rains, the force of the water hitting the ground is deflected. In most cases, if the slope soil is deeper, a mix of deep-rooted plants like  bougainvillea and shallow-rooted plants like monkey flowers or sagebrush are needed to secure the top soil to the bottom rock. Groundcover best prevents the surface erosion. English ivy is a good example of how many plants installed into the slope will bind the surface tightly and cover it all with dense foliage. This planting strategy must be irrigated with broadcast sprinklers. Creeping shrub, like prostrate rosemary has just one stem that spreads out in every direction with a carpet of foliage. That coverage slows the raindrop energy too. Shrubs are watered only at the t runk, which is  better suited to drip or bubbler irrigation for water conservation. Hydroseeding is a method of sowing seed on a large scale for immediate coverage. It is often required at the completion of a project to provide soil holding capacity until other plants mature. This quick-cover reduces the problem of sediment and runoff the first rainy season after completion. It is common to plant the slope with container grown shrubs and groundcovers, then spray the hydroseed right over the top of them for both short and long term solutions. A local contractor is the best resource for solving erosion control issues for residential  building sites. Knowledge of local soils, rainfall and plants that thrive in the microclimate as well as irrigation techniques aids in creating a palette of plants for the 50

slope. The best planting design solutions include a diversity of plants. (Gilmer, Landscaping Network) 4.4.3. Geotextiles for Erosion Control

 Newly graded slopes are vulnerable before and after planting. Erosion control plants take time to become established and fill in both above and below ground. Until this happens the slopes will be temporarily exposed to erosion. For that time, geotextiles should be used, which are man-made materials, laid on the earth and pinned into  place. Because they are biodegradable, landscaping can be done right through it knowing that by the time plants fill in the fabric will decompose and eventually disappear. Following are the different types of geotextiles: Burlap: Used for immediate erosion control on very steep slopes prone to disintegration. Jute mesh: Large square jute mesh is the standard for landscaping because it is easily  planted through the grids. Coir mat: A byproduct of coconut processing. Coir has great water holding capacity and resists decomposition for more long term use. (Gilmer, Landscaping Network)

4.5. Conclusion Slopes offer a great challenge than flat ground when it comes to landscaping. Planning a garden with slopes will surely be a challenge, but changes of level certainly give any garden added interest, and add an extra aspect to sloping landform design. Factors to be considered while planning a landscape on slope include drainage, soil, access and maintenance, rainwater and runoff management, irrigation and other issues. Whether it is a natural undisturbed slope or one composed of cutand-fill, there are five essential principles that should be taken care of while designing on slopes. Different ways of landscaping is also discussed in this chapter which includes terracing, tiering, change in levels and rock landscaping. Hillside retention and erosion control are two key issues in slope landscaping which is also taken into consideration.

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CHAPTER-5.

CASE STUDIES OF DIFFERENT BUILDINGS

ON SLOPING SITES Buildings on sloping sites have different architectural and structural considerations. Case study of different residential buildings makes better understanding about the incorporation of contours into the building design, architectural features, and effective structural systems.

5.1. Car park house, Los Angeles This modern house on stilts has one level floor plan with flat roof at street level as a carport and deck terrace space (see  Figure 5.1). Skylights element also installed on the roof for better lighting inside this rectangular modern house on stilts. Floating structure used for efficiency because of difficult terrain topography and create single access for the house. (ArchInspire) From street to this house a bridge is built. This modern house on stilts plan accommodate single space for living-kitchen-dining (kitchen area placed in the center of interior), three bedrooms, two bathrooms, laundry area and balcony spaces. The exterior of this modern house on stilts is gray compare to its whiteness interior design. Although there are glass walls installed along side of balconies area, skylights installation still needed to make sure natural light intensity inside this modern house on stilts.

Fi gure 5.1: Car park h ouse buil t on sloping site (ArchInspire)

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5.2. Family house, Prague The 5+1 room detached house is located in the residential area of a small town close to Prague. Its narrow and sloping site is shaping the building. (see  Figure 5.3)  The form gently follows the contours of the slope in order to maximize the connection of interior with exterior (Grido Architektura and Design). Architect tried to utilize the contours upto is full extent. (see Figure 5.2) Lining up the rooms of the house along the north edge of the site is like stringing  beads on an imaginary axis of circulation passing through all of the interior spaces. Living room and dining room are central, with the highest ceilings and are tightly connected to the garden. The other rooms are arranged alongside forming a shape  bended at the ends. Timber frame construction is covered by the metal cladding protecting the north facade. The south facade is open and articulated, offering an active zone. The building skin is rough and protective from the outside but smooth and warm inside. Aiming to design a low energy house, a well-insulated timber frame construction, south-facing orientation and active and passive solar design was considered. By collecting the sunlight through the large south-facing windows the wintertime passive heating is maximized. In order to minimize undesirable solar gain, there are no east and west-facing windows. The roof overhangs are sized to allow winter sun in and keep summer sun out. Forced air ventilation with heat recovery is combined with the low temperature heating system. Total annual energy consumption is below 50 kWh/m2. The house represents an accomplished dream of a larger family  –   living in an open sunny house with panoramic views on the surrounding mountains.

 (Grido Architektura and Design) F igu re 5.2: Conceptual sketches developed by the ar chit ect 

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F igu re 5.3: View of the house (top), timber fr ame constr ucti on (bottom left), sections (bottom righ t) (Grido

Architektura and Design)

5.3. Apartment block, North-East Italy Positioned beside the Dolomites, the three-storey Dolomitenblick building contains six holiday homes that each face north-east towards the mountains. A diagonal recess slices down the centre of the facade, separating the balconies of different apartments and breaking down the volume of the building. (Plazma Studio) Each private unit is designed to get a maximum of privacy- through the division of the whole building volume into 2 parts, through the stepped balustrades which avoid insight from the above unit and from the passing by street. Each apartment gets an extension of the internal living area by a covered sun and view facing terrace which at each floor ends in a small private garden. From the cut at either side a strip unfolds that forms the balustrade of a generous covered balcony and ends into the surrounding topography. (see  Figure 5.4)  The whole facade also slopes backwards to match the incline of the sloping land, finishing

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with an asymmetric interpretation of a traditional gabled roof, which the architects were asked to incorporate by the local planning authorities. Inspired by local farmhouses, the architects used larch to clad the walls behind the  pre-oxidized copper balconies, as well as the floors and walls inside each apartment. Larchwood facades blend into the natural surroundings. Focus was given to the desi gn of the copper balustrades which start from the natural topography, grow, become  balustrades, attach to the building where the gap defines the volume, peel again off and end finally in the surrounding topography. Local larch wood defines internal and external living areas. Floor to ceiling glazing allows the maximum view and energetic gain as directed to south, external sun blinds and the overhangs of the above balconies minimize overheating during summertime. Sitting at the edges of a residential area with a very eclectic and non-coherent appearance we focus to contrast these surroundings by simply generating a volume which grows out of its natural surrounding topography and blends again into it, by minimizing the used materials to a very local, almost vernacular code: larch wood and pre oxidized copper. Both the copper and the larch wood are exposed to a natural change of color by the atmospheric influence of sun, rain and snow. They also made various depressions into the ground, adding low-level windows and a tunnel leading into an underground parking area beneath the building. The volume has  been developed mainly from its pragmatic functional request to host 6 independent apartments with one common circulation: through a cut that marks the main access and the division of the units the volume is splitted into 2 halves. Besides its functional meaning this incision becomes the main defining element of the building.

 (Plazma Studio) Fi gure 5.4: The thr ee-storey Dolomitenbli ck buil ding 

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5.4. Stepped house, Spain Elusive scenery and interesting architecture are the advantages to building a house on a sloping site. This tiered home designed by Allford Hall Monaghan Morris in Spain is one of the good example. (see  Figure 5.5). This stepped house allows each level a grand view of the sea. House is built in the oak forests and steep meadows of the Santa Lucia Mountains. The top level is the main entry point to the home. (see  Figure 5.6 )  Full sized windows line the back walls that face the nature preserve. The side view shows the overall scope of the proposed buildings. From top to bottom, the regression is a garage, then steps and gardens leading down to the main living quarters, and a pavilion and steps leading down further to a garden and small infinity  pool. This type of housing layout is perfect for a sloping narrow site. (Eva Designs, 2014)

F igu re 5.5: Tiered home on slopi ng site in Spain (l eft), view showi ng arr angement of spaces (ri ght) (Eva

Designs, 2014)

F igu re 5.6: Side view of home showing stepped appearan ce (Eva Designs, 2014)

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5.5. Conclusion Buildings on sloping sites have different architectural and structural considerations. So, the study of buildings in different types of terrains would enhance the understanding of behavior of the building towards the landform. The context given in the chapter is aimed at achieving attractive and functional places through better design, better construction techniques, proper use of building materials, suitability of landslopes for different buildings.

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 DIY network . (n.d.). Retrieved May 2, 2014, from Rock Landscaping Ideas : http://www.diynetwork.com/outdoors/rock-landscaping-ideas/pictures/page4.html Eva Designs. (2014, Februry 3).  A Home Built on a Slope. Retrieved from http://www.evadesigns.com/interior-design/architecture/a-home-built-on-aslope Federal Highway Administration. (Updated: 02/10/2014).  Designing Sidewalks and trails for access. USA: Federal Highway Administration. Gilmer, M. (n.d.).  Landscaping Network . Retrieved May 2, 2014, from Hillside Landscaping Ideas: http://www.landscapingnetwork.com/hillsides/ Gilmer, M. (n.d.).  Landscaping Network . Retrieved May 2, 2014, from Erosion Control

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Residential

Hillsides:

http://www.landscapingnetwork.com/hillsides/erosion-control.html Grido Architektura and Design. (n.d.). Retrieved May 2, 2014, from Family house in Cernocise: http://www.grido.cz/en/project/house-in-cernosice/ H.S. McKay, C. J. (2000). Creating Places-achieving quality in residential developments. Department of Environment.  How to Build on a Sloping Site. (n.d.). Retrieved March 23, 2014, from http://www.homebuilding.co.uk/advice/beginners/plots/build-sloping-site HRO. (n.d.). ARTICLE 55. GRADING AND EROSION CONTROL. Retrieved April 4, 2014,

from

Sec.

33-1067.F.

Design

guidelines

for

HRO

district:

http://www.qcode.us/codes/escondido/view.php?topic=33-5533_1067_f&frames=on  North Tipperary County Council. (2009).  Rural Design Guide for Individual Houses in the Countryside. North Tipperary County Council. Plazma Studio. (n.d.).  Plazma Studio. Retrieved Februry 10, 2014, from Dolomitenblick

by

Plasma

Studio:

http://www.dezeen.com/2013/01/02/dolomitenblick-apartment-block-by plasma-studio/

59

 Rock Landscaping Ideas  –   Flat and Sloping Sites. (n.d.). Retrieved April 4, 2014, from

http://www.gardeninginfozone.com/rock-landscaping-ideas-flat-and-

sloping-sites (n.d.). Slope Stabilization and Stability of Cuts and Fills- LOW-VOLUME ROADS  BMPS. Tweed Shire Council. (n.d.). Sloping Sites- Your Guide to building a house. Washburn, B. (n.d.).  Ideal Home Garden. Retrieved May 2, 2014, from Terraced Garden

Design

Ideas:

http://www.idealhomegarden.com/outdoor-

living/terraced-garden-design-ideas/

ANNEXURE Tabl e 1 : Common stable slope rati os for varyin g soil /rock condi tion s (Slope Stabilization and Stability of Cuts

and Fills- LOW-VOLUME ROADS BMPS)

Soil/Rock conditions

Slope ratio

Well cemented soil

¼:1 to ½:1

Very fracture rock

1:1 to 1 ½:1

Loose coarse granular soil

1 ½:1

Heavy clay soil

2:1 to 3:1

Heavy clay soil or seepage areas

2:1 to 3:1

Hard angular rock fills

1 1/3:1

Low cut and fills (