3. Applied Geomorphology (Akshay)

Geography for IAS

Akshay Hajare

Contents Part 1 Applied Geomorphology Part 2 Economic Geology And Environment Part 3 Geohydrology

Part 1

Applied Geomorphology

Geomorphology has traditionally focused on the study of landforms and on the processes involved in their formation. Applied geomorphology is the practical application of this study to a range of environmental issues, both in terms of current problems and of future prediction. Applied geomorphology provides a strategic tool for informed decision-making in public policy development and in environmental resource management. Key areas of application include specific environmental settings, such as the coastal zone or dry-land environments; the impacts of land use and management practice on Earth surface processes; and areas susceptible to natural hazards. The main theme of applied geomorphology is to investigate the impact and changes brought in natural environment systems and economic activities, problems arising from the same and to suggest suitable remedial measures thereof; to study the impact of geomorphological processes/ environmental processes on different aspects of human society and human activities; and to attend problems of resource management and monitor changes in geomorphic /environmental systems including both landscape characteristics and landform processes consequent upon human economic activities Definition: “Applied geomorphology may be defined as the application of geomorphologic understanding to the analysis of solution of problems concerning land occupancy, resource exploitation, environmental management and planning” - D.K.C Jones (1980) The aims of Applied Geomorphology are • to assist in the efficient discovery, assessment and wise management of the earth's finite resources, • to prevent environmental deterioration and • to avoid or prevent natural hazards. Application of geomorphology can be divided into two categories (R.J.Chorley) I) Man as geomorphic agent, in terms of this inadvertent and planned effects on geomorphic processes and forms. II) Geomorphology as an aid to resource evaluation, engineering, construction and planning.

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Geography for IAS

Akshay Hajare

Early Works in AG Thornbury (Principles of Geomorphology, 1950) stressed the need for applying geomorphology to mineral and oil exploration, hydrological studies and engineering projects. International Geographical Union(IGU) • Appointed a commission on Applied Geomorphology in 1956. • Appointed commissions on 1) Man and Environment, 2) Geomorphological Survey and Mapping, 3) Present day geomorphological processes and experiments in geomorphology in 1968. UNESCO In its concern for man and environment has acknowledged the importance of applied geomorphology in its quarterly publication Nature and Resources, being published since 1965 as well as in the publications of the International Hydrological Decade (IHD) Some Prominent Areas of Applied Geomorphology ➔ Hazard and Risk Natural hazards such as volcanic eruptions, earthquakes, and mudflows present a significant risk to the population of the surrounding area. Geomorphological mapping can be used to assess the present condition of the landscape and provide a hazard map. The expression of a disaster may result in one settlement having significantly different risk assessment. For example, a volcanic eruption may pose a threat from volcanic ash and lava flows, pyroclastic flows, and bombardment from superheated volcanic bombs or associated hazards such as mudflows, depending on topography, soil cover, type of eruption, and predominant wind direction. This application of geomorphological analysis is of significant interest to the emergency services and the insurance industry. ➔ Coastal Landforms Over 60 per cent of the world's population live in the coastal zone in environments ranging from coral atolls, reclaimed or natural wetlands, dune-backed beaches, and barrier islands to cliff tops. Settlements under threat from coastal erosion and flooding from storm events, sea surges, and rising sea level lobby for protective engineering measures to prevent loss of property, livelihood, and life. Geomorphology has several applications in settings of this type. An understanding of coastal landforms and the processes acting upon them can be used to map areas at risk from cliff failure, beach erosion, and flooding. This approach is of interest to potential developers and the insurance industry and is an important tool in environmental impact assessment (EIA). An understanding of the geomorphology of the coastal zone can also be used to

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Geography for IAS

Akshay Hajare

predict the effects of modifying the coastal system. The installation of groynes, breakwaters, or protective sea walls has knock-on effects on the natural circulation of water and sediment in the near-shore environment. Artificially stabilizing cliffs to prevent erosion may seem the obvious solution for cliff-top dwellers, but a geomorphological evaluation might predict that this approach could starve beaches of the sediment provided by natural cliff fall, with a consequent impact on longshore drift of sediment, and would relocate the focus of erosion further along the coast. The nature of the problem may thus change from cliff failure at one site to beach erosion and subsequent flooding at another. An understanding of the nature and complexity of coastal dynamics is thus an essential component of a coastal-zone management strategy and is important in predicting the future effects on coastal landforms of a rise in sea level. ➔ River Management Strategies River-management strategies for flood alleviation have often adopted engineering solutions concentrated in particular river reaches, which are usually in areas of urban development. Reach-specific intervention measures include lining the natural channel with concrete to prevent erosion and bank instability, channel straightening to force flood water to flow rapidly through particular reaches, and flow-control structures such as sluice gates and reservoirs to control water level. These artificial measures are not always successful in preventing flooding and erosion within the river catchment, and natural sections further downstream may be overwhelmed by the river at peak flood. The engineered reaches of rivers often become a sterile landscape because fast-flowing water in a concrete-lined channel, with minimal variation in water depth and channel cross-section, provides a poor habitat for wetland flora and fauna. Geomorphology has been applied to „river restoration‟ to recreate an integrated river management strategy within artificially created river systems, maximizing biodiversity while controlling river-flow conditions. Applied geomorphology uses a holistic approach to river response at a catchment-wide scale; the basis here is an understanding of the relationships between river form and process, sediment transport, and the important role of river-bank (riparian) vegetation.

Applied Geomorphology has several branches and it is related with various science, thus it is multi disciplinary by itself. Recently sub-branches have been recognized: 1. Economic Geology, 2. Geohydrology, 3. Environment etc.

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Akshay Hajare

Geography for IAS

Part 2

Economic Geology And Environment

The theme of economic geology includes application of various geomorphic principles to obtain economic benefits for the purpose of development, without negatively affecting the environment. Economic geology is concerned with earth materials that can be used for economic and/or industrial purposes. These materials include precious and base metals, nonmetallic minerals, construction-grade stone, petroleum minerals, coal, and water. The lithology and the regional structure of the rocks are reflective of the possibilities of economic minerals present in them and provide an opportunity for their exploitation. Mineral resources are concentrations of minerals significant for current and future societal needs. Ore is classified as mineralization economically and technically feasible for extraction. Some ores have direct surface expression either as relief features or as outcrops of ore or residual minerals. If the geomorphological expression of a specific ore body can be identified for a particular area, it may become relatively easy to locate similar ore bodies. Either directly or indirectly rocks have great economic value. On the nature of bedrock depends to a large extent, the soil which is produced by weathering process. The whole question of man's vital water supply is bound up with the nature of the rocks. From rocks many substances of great importance are derived, these include fuel like coal and mineral oil, building materials, rock-salt etc.

Sr No Mineral

Lithology/Rock Structure

Region Examples

1

Tin Mining

Placer/ Paleozoic Plateau

Malaya plateau (Kinta & Kelang) Bolivian plateau (Potosi & Oruro)

2

Gold

Veins of Magma/Pre Cambrian deposits Placer

South African Plateau (hard rock) River Valley(Placer) – Suwarnarekha, Son

3

Bauxite

Laterite Deposits Gondwana Shield Rocks Note:Bauxite in area of high leeching in tropics

Cape York, Arnhem (Australia) Orissa Hills

4

Hematite

Pre Cambrian Sedimentary Dharwar rocks- Singhbhum, rocks Mayurbhanj Iron Ore Range(USA)

5

Ilmenite(titanium) Sand ore deposits

Malabar Coast

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Geography for IAS 6

Monazite(thorium Sea/wave built platform ) Placer deposits

Malabar Coast

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Petrolium

Persian Gulf (geosyncline)

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Lead, Silver, Zinc Veins of pre-cambrian magma and pre-cambrian sedimentary deposits

9

Limestone + Dolomite

Cretaceous rock formation Karst region Yugoslavia Note: In latin “creta” Alsace(France) means chalk Scotland

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Uranium

Pre-cambrian rocks Exumed surfaces/Uplifted Peneplanes

Folded sedimentary rocks under sub-marine conditions

Udaipur Ozark Plateau(USA)

Pre-Cambrian: Tummalapalle (Kadapa dist, AP) Uplifted Pene: Chota Ngp Plateau

Mineral Ores Metals are found usually in the form of a metal-liberous mineral known as ore. Many mineral ores are associated with former igneous activity so that the occur as veins occupying fissures and cavities in the rocks. Sometimes the various agents of erosion, working on the parent deposits, may wash out an deposit elsewhere either the metallic ores or even the parent material. Owing to their high density, stream actions sometimes sorts and concentrates the metals in beds of gravel or in alluvial flats, known as placers; gold, tin and platinum may occur in this way. Figure: Gold Placer Deposits

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Understanding of geomorphic principles and history is needed for : •

Highways, railways and airports Topography obviously plays important role in determining the most feasible highway route. Eg The Srinagar – Leh highway makes full use of the physiographic corridor provided by the valleys of the Jhelum. A karst terrain is marked by near-waterless surface with sinks and underground caverns. The sink holes, however, are liable to flooding during heavy rains. A route over karst plain therefore requires repeated fill.

•

Multipurpose dams and reservoirs for water supply, irrigation power and flood control Dam construction in a limestone terrain is likely to result in leakages and water is likely to seep into solution channels and emerge as seepages below the dam. On the other hand, impervious bed-rock will provide a dependable and adequate reservoir. In planning a multipurpose project many major factors have to be considered including the geomorphology and geology of the area, its hydrological characteristics, ways of integration and co-ordination of all various uses of water, such as for irrigation and flood control, hydel power, navigation, domestic and international water supply, recreation, fishing and wild life etc.

•

Dykes, sea-walls etc, built to protect home sites, industrial structures, harbors etc In many cases the effects of human structures and developments at the coast have been historically integrated into our understanding of coastal geomorphology. Eg. Sea-walls being constructed in a fashion that coastal marshes provide them protection form storm and wave erosion.

•

Regional Planning Planning requires suitable planning unit in terms of spatial unit, which poses a great problem before the planners and decision makers. Administrative unit cuts across the physiographic unit and therefore the continuity of natural resources is broken. Even if the regional planning is attempted be selecting administrative units as planning units, information of topographic details, soils, natural resources etc may be helpful for the purpose.

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Geography for IAS

•

Akshay Hajare

Hazard Management Geomorphic knowledge helps in the identification, prediction and assessment of probable effects and management of natural geomorphic hazards. Constant measurement of temperature of crater lakes, monitoring of gases coming out of craters, monitoring of changes in the configuration of dormant or extinct volcanoes by lasers, measurement of local gravity and magnetic fields and their trends etc. help in making predictions of possible eruptions in the areas having past case histories of volcanism. Channel geometry, channel morphology and channel pattern river metamorphosis, bank morphology etc may help in controlling river floods through several flood control measures.

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Geography for IAS

Part 3

Akshay Hajare

Geohydrology

It is a special branch of study which combines geology and hydrology and it studies all surfacial and sub-surfacial water and hydrological system including their movement, circulation and their impact Water Table Geohydrological water includes 1. Fossil water, 2. Hygroscopic water, 3. Capillary water, 4. Vadose zone and 5. Phreatic Zone 1. Fossil water: Water which is trapped in magma or igneous rocks and cannot be utilized. 2. Hygroscopic: Microscopic water which binds/holds the soil. This cannot be used by the plants it just provides structure to the soil. 3. Capillary water: It is found in veins of sedimentary rocks. Important for soil moisture, agriculture and plant growth. 4. Vadose: It is seasonal in nature, found in the zone of intermittent saturation, which is zone of water filled during rainy season but air filled during the dry season. It is also called the unsaturated zone. 5. Phreatic: It is zone of permanent saturation where throughout the year aquifer is water filled. This surface normally coincides with the water table. Figure: Cross-section of a hill slope depicting the aquifer and the water table

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Geography for IAS

Akshay Hajare

Geohydrology is concerned with the movement of water and the related processes and associated features. In the zone of limestone they create a unique topographical landform termed as karst region. Karst Region Generally karst region have a bleak landscape, occasionally broken by precipitous slopes. There is general absence of surface drainage as most of the surface water has gone underground. Streams rising on other rocks only flow over limestone for a short distance and then disappear underground. For the greater part of their course, they cut their way along the joints and fissures of the rock wearing out a system of underground channels. When water penetrates to the base of limestone and meets non-porous rocks it re-emerges onto the surface as a spring or resurgence. Limestones are well jointed and it is through these joints and cracks that rainwater finds its way into the underlying rock. Progressive widening by solution (limestone + carbon dioxide in water) enlarges the cracks and limestone pavement is developed. The limestone pavements may have been formed beneath the soil and are now exposed by the removal of the soil cover. On surface of limestones are numerous swallow holes – small depressions carved out by solution where rain-water sinks into the limestone at a point of weakness. They are also know as sink holes. Once water has sunk into the limestone it etches out caverns and passages along joints or bedding planes. When subterranean streams descend through swallow holes to underground passages, the region may be honeycombed with caves and caverns, some containing ponds and lakes. The most spectacular underground features that adorn the limestone caves are stalactites, stalagmites and pillars. Stalactites are sharp, slender, down-ward growing pinnacles that hang form the cave roofs. The ware carries calcium in solution and when this lime-charged water evaporates, it leaves behind the solidified crystalline calcium carbonate. As moisture drips from the roof it trickles down the stalactite and drops on the floor where calcium is deposited to form stalagmites. They are shorter, fatter and more rounded. Over a long period, the stalactite hanging from the roof is eventually joined to the stalagmite growing from the floor to form a pillar. Eg are Batu caves, Kuala Lumpur; Postojna caves, Yugoslavia etc.

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Geography for IAS

Akshay Hajare

Figure:Karst Region

Application of Geohydrology 1. 2. 3. 4. 5. 6.

Urbanization Agriculture Construction Engineering Geohydrology and Afforestation Geohydrology and Reclamation of land Geohydrology and Mineralogy (Petroleum etc)

References Alok Ranjan's Notes & Booklet Wikipedia GC Leong Other Internet Sources 10