What are the most effective GIS techniques for floodplain mapping?

1 Data Sources

Gathering and processing data to describe the hydrological, topographical, and socio-economic characteristics of a study area is the first step in floodplain mapping. Common data sources include Digital Elevation Models (DEMs) derived from satellite imagery, aerial photography, or lidar surveys; hydrological data such as rainfall, streamflow, and water level measurements; land use and land cover data extracted from remote sensing or field surveys; and socio-economic data collected from census, surveys, or databases. These sources must be imported, converted, and projected into a common GIS format and coordinate system for further analysis.

3 Flood Hazard Assessment

The third step in floodplain mapping is to assess the flood hazard, which is the probability and severity of flooding in the study area. This can be achieved by using GIS techniques such as flood frequency analysis, flood extent mapping, flood depth mapping, and flood velocity mapping. These techniques use statistical methods, raster or vector operations to estimate recurrence interval, delineate boundaries, calculate water depth and velocity at each location within the flooded area. This can help identify areas and features that are most vulnerable to flooding and quantify the flood hazard.

4 Flood Impact Analysis

The fourth step in floodplain mapping is to analyze the flood impact, or the potential damage and loss caused by flooding in the study area. This can be done through GIS techniques such as flood damage assessment, which uses economic methods to estimate the direct and indirect costs of repairing or replacing the infrastructure, buildings, and assets affected by flooding. There is also flood risk assessment, which uses probabilistic methods to estimate the expected annual damage or loss due to flooding based on flood hazard and damage data. Additionally, there is flood vulnerability assessment, which uses social methods to estimate the exposure and sensitivity of the population and communities affected by flooding. Lastly, there is flood resilience assessment, which uses adaptive methods to estimate the capacity and potential of the population and communities to cope with, recover from, and adapt to flooding. These GIS techniques can help evaluate the consequences of flooding and prioritize flood mitigation and adaptation measures.

5 Flood Mitigation Planning

The fifth step in floodplain mapping is to plan for flood mitigation, which is the action or strategy to reduce or prevent the flood hazard or impact in the study area. This can be done by using GIS techniques, such as flood control design, flood zoning regulation, flood warning systems, and flood insurance schemes. Flood control design uses engineering methods to design and optimize structural measures based on hydrological and hydraulic data. Flood zoning regulation uses planning methods to regulate and restrict land use based on land use and land cover data. A flood warning system utilizes communication methods to monitor and alert people about the occurrence and severity of floods based on hydrological and meteorological data. And a flood insurance scheme uses financial methods to compensate and incentivize people for the flood damage or loss based on flood risk and insurance data. By utilizing GIS techniques, you can formulate and implement effective flood mitigation options and assess their effectiveness and efficiency.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?