Step 3: Risk Assessment

A basin flood management plan has to start with assessing the present and future flood risks. For risk assessment it is essential to develop an understanding of the three constituents of flood risks.

  • The magnitude of the flood hazard expressed in terms of frequency and severity (depth, extent and duration of inundation and relative velocities)
  • The exposure of human activities to flooding
  • The vulnerability of the elements at risk

Hazard Assessment: Understanding of flood hazard require hydro meteorological analysis; hydrologic and hydraulic simulation of surface runoffs, floods and inundations; and mechanism of flooding. (It may also require a simulation and analysis projected conditions of land use change, future developments (e.g., urbanisation, infrastructure development etc) and the future trends of hydro-meteorological phenomenon due to climate variability or change.) Flood inundation maps developed for different scenarios help understand and communicate with different stakeholders. Such flood maps would be the basis for developing flood risk scenarios based on various development alternatives, social and economic conditions.

Exposure Assessment: Analysis of exposure requires knowledge of the existing land use and the kind of activities that are undertaken in these areas. This analysis is useful in order to consider the regulatory mechanism as oneof the possible alternatives for risk reduction. It is also important to assess the exposures based on the planned future land uses contemplated.

Vulnerability Assessment: Analysis of the vulnerability of the section of the society exposed to flooding will show why and to what extent they are affected. It may be attributable to the social factors (poverty, livelihoods, gender, weaker social groups, minority and ethnic groups) and the attributing vulnerability conditions (physical, constitutional, motivational) of the flood plain occupants. A demographic analysis based on surveys may be required for the purpose. A close involvement of the communities in these assessments along with the experts would give credence to such studies.

Estimation of damage in monetary and non monetary terms for given condition is required for assessment of flood risk. This forms the basis for economic analysis of various options and deciding the priority of various basin flood management options. Outcomes of these analyses should also be translated into an understandable manner for the public to be able to get the common understanding among all stakeholders concerned.

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