Flood risk assessment

A flood risk assessment (FRA) is an assessment of the risk of flooding from all flooding mechanisms, the identification of flood mitigation measures and should provide advice on actions to be taken before and during a flood. The sources of water which produce floods include: groundwater, surface water (rivers, streams or watercourses), artificial water (burst water mains, canals or reservoirs), sewers and drains, seawater.

For each of the sources of water, different hydraulic intensities occur. Floods can occur because of a combination of sources of flooding, such as high groundwater and an inadequate surface water drainage system. The topography, hydrogeology and physical attributes of the existing or proposed development need to be considered. A flood risk assessment should be an evaluation of the flood risk and the consequences and impact and vulnerability.

In the UK, the writing of professional flood risk assessments is undertaken by Civil Engineering Consultants. They will have membership of the Institution of Civil Engineers and are bound by their rules of professional conduct. A key requirement is to ensure such professional flood risk assessments are independent to all parties by carrying out their professional duties with complete objectivity and impartiality. Their professional advice should be supported by professional indemnity insurance for such specific professional advice ultimately held with a Lloyd's of London underwriter.

Professional flood risk assessments can cover single buildings or whole regions. They can part of a due-diligence process for existing householders or businesses, or can be required in England and Wales to provide independent evidence to a planning application on the flood risk.

In the United States of America, flood maps come from the Federal Emergency Management Agency (FEMA). They work with all levels of government in each part of the country to establish which areas have any risk of flooding. Risk Mapping, Assessment, and Planning (Risk MAP), is the process used to make Flood Insurance Rate Maps. These maps break down what communities can do to keep their surroundings safe, and get through flooding disasters in 4 phases: Discovery, Analysis & Mapping, Preliminary Flood Mapping Release, and Map Adoption. The goals are to identify, assess, communicate, and reduce risk.

These federal maps are used by local governments to inform civilians on where their evacuation routes are and how they should be read based on zones.

Through flood watches and warnings, civilians are informed that their specific location either has a possibility of being impacted, or will be impacted during a certain time slot. It is constantly updated and monitored by the National Weather Service. "The National Weather Service will discuss flood and flash flood potential in daily hazardous weather outlooks and in the graphical weather story on National Weather Service websites." Vehicles are the top causes of death in flood situations. Many think their vehicles can withstand water on roads, but no one knows what is under the water, or if the roadway is compromised. Water can rise at extremely high speeds, and being in a confined area, such as a car, is not recommended. Turn around and get out of the area as safe and quickly as possible.