Highway Engineering

FLOOD MITIGATION PROGRAMS WHAT IS MITIGATION? Mitigation is the effort to reduce loss of life and property by lessening the impact of disasters. Mitigation is taking action now—before the next disaster— to reduce human and financial consequences later (analyzing risk, reducing risk, insuring against risk). Effective mitigation requires that we all understand local risks, address the hard choices and invest in long-term community well-being. Without mitigation actions, we jeopardize our safety, financial security, and self-reliance. Federal Emergency Management Agency (FEMA)'s mitigation programs help reduce the impact of events—and our dependence on taxpayers and the Treasury for disaster relief. FEMA's Federal Insurance and Mitigation Administration (FIMA) manages the National Flood Insurance Program (NFIP) and implements a variety of programs authorized by Congress to reduce losses that may result from natural disasters. Effective mitigation efforts can break the cycle of disaster damage, reconstruction and repeated damage. FEMA's mitigation and insurance efforts are organized into three primary activities that help states, tribes, territories and localities achieve the highest level of mitigation: Risk Analysis, Risk Reduction and Risk Insurance. Through these activities and FEMA's day-to-day work across the country, communities are able to make better mitigation decisions before, between and after disasters. 1. Risk Analysis Government agencies must understand the full impact of natural hazards using applied multi-hazard engineering science and advanced technology in order to effectively plan to reduce natural hazard effects.   

Flood Hazard Mapping National Dam Safety Program Multi-Hazard Mitigation Planning

2. Risk Reduction The goal of risk reduction is to reduce the risk to life and property, which includes existing structures and future construction, in the pre and post-disaster environments. This is achieved through regulations, local ordinances, land use and building practices and mitigation projects that reduce or eliminate long-term risk from hazards and their effects.     

Hazard Mitigation Assistance (HMA) Grant Programs Floodplain Management National Earthquake Hazards Reduction Program (NEHRP) National Dam Safety Program Building Science

3. Flood Insurance The National Flood Insurance Program (NFIP) goal is to reduce the impact of flooding on private and public structures by providing affordable insurance for property owners. The program encourages communities to adopt and enforce floodplain management regulations, which will mitigate the effects of flooding on new and improved structures. The NFIP is helping communities reduce the socio-economic impact of disasters by promoting the purchase and retention of both Risk Insurance and National Flood Insurance. 

National Flood Insurance Program (NFIP)

Flood Mitigation Measures can be divided into three (3) main areas:   

Control over the river; Control over the land; Other measures.

Control Over the River In order to achieve control over the flow and height of the water carried by the river, the channel, flood plain or watershed must undergo some physical alterations. These include:   

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Construction of dams, retention basins or reservoirs on mainstreams or tributaries to store excessive water and release it gradually after the threat has passed; Levees or floodwalls can be constructed to confine flood waters to a floodway, thereby reducing flood damage; Channel improvements, which include, straightening to remove undesirable bends, deepening and widening to increase size of waterways; clearing to remove brush, trees and other obstructions; lining with concrete to increase efficiency. Watershed Treatment can also be employed to help the soil on slopes to become more absorbent of rainfall until flood heights have receded. Watershed Treatment involves, crop rotation, construction of terrace, contour strip cropping; selective planting and reforestation.

Control Over the Land To protect against flooding, certain Land Use Policies were developed. Below is a list outlining the measures undertaken within these policies. 

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Designated Floodways and encroachment lines o These are the lateral boundaries of the floodway where no construction or land filling should be permitted. This is done to ensure that the flow of water is not obstructed. Zoning o This is a legal tool used by governments to control development in areas which are or are likely to become prone to flooding; Subdivision Regulations o These specify the manner in which land may be divided. Typical provisions show the extent of the flood plain on maps. Floodway limits or encroachment lines prohibit filling in channels and floodways that restrict flow and require that each lot contain a building site with an elevation above the flood level. Building Codes o These are standards for construction of buildings and other structures and, if enforced, can reduce damages to buildings in flood-prone areas. Some requirements include, the establishment of basement elevations and first flood elevations consistent with potential flood levels, ensuring that buildings have adequate structural strength which would likely withstand water pressure or the high velocity of flowing water, prohibiting the use of equipment that might be hazardous to life when submerged and installing proper anchorage to prevent the floatation of buildings.

Additional Mitigation Measures These include flood proofing, flood forecasting, warning and evacuation systems. 

Flood Proofing

This is a combination of structural changes and adjustment to properties which can be used in new or existing construction. Action includes seepage control, protective coverings, elevation or raising anchorage and under pinning. Flood Forecasting o This is reliable, accurate and timely forecasting of floods, coupled with timely evacuation to save lives and reduce property losses. Temporary Evacuation o This removes persons and property from the path of flood waters. Permanent Evacuation o This removes an affected population from areas subject to inundation. This involves the acquisition of lands and the removal of developments. The acquired lands can be used for agriculture, parks or other purposes that would not interfere with flood flows or result in material damage. Flood Insurance o This assists by compensating for flood damage. Insurance rates should realistically reflect the flood risk in order to avoid encouragement of improper development of flood plains. o

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HAZARD MITIGATION ASSISTANCE PROGRAMS FEMA’s Hazard Mitigation Assistance (HMA) grant programs provide funding for eligible mitigation activities that reduce disaster losses and protect life and property from future disaster damages. Currently, FEMA administers the Hazard Mitigation Grant Program (HMGP), the Flood Mitigation Assistance (FMA) Program, and the Pre-Disaster Mitigation (PDM) Program.   

HMGP assists in implementing long-term hazard mitigation measures following a major disaster PDM provides funds for hazard mitigation planning and projects on an annual basis FMA provides funds for projects to reduce or eliminate risk of flood damage to buildings that are insured under the National Flood Insurance Program (NFIP) on an annual basis

FEMA’s HMA programs provide funding for eligible mitigation activities. Commonly funded mitigation activities include: 

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Acquisition – commonly known as a “buyout” is the most permanent form of mitigation. It removes the home completely and the land is converted into open space (e.g. a park). The acquisition process is strictly voluntary. FEMA encourages all homeowners in affected communities to be sure they get all of the information needed about buyouts so they can make the best decision for their families and communities. Dry Floodproofing – techniques applied to keep structures temporarily watertight (e.g. sealing a structure to keep floodwaters out) Elevation – involves physically raising an existing structure to thebase flood elevation level or higher Minor Localized Flood Reduction – lessens the frequency or severity of flooding by creating retention/detention basins Safe Room Construction – designed to provide immediate life-safety protection for limited at-risk population that cannot evacuate out of harm’s way before an event