The confluence of climate change, accelerating development, and other factors has led to a steep increase in the frequency and costs (human and financial) of natural disasters around the country and the globe. With our expertise in GIS and a strong background in earth system science, GISmatters can provide cost-effective site-specific and regional assessments of natural hazard risks. These are ideal when detailed and expensive hydrologic or geotechnical assessments are not needed, or to prioritize their implementation at various sites.

Natural Hazards: Floods

Terrain model with/without floodzones

Landsat image with/without floodzones

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Our flood models are effective at estimating floodzones based on gridded terrain models. Estimates are made for a particular 24-hour rainfall event, which can be prescribed or determined statistically from historical rainfall records for a location or region. Flooding is modeled throughout an entire watershed catchment, and generates a floodmap for each event whose accuracy varies with the resolution and quality of the underlying terrain data. We can work with off-the-shelf, public domain terrain data (such as that available from state or municipal GIS agencies), or with proprietary data, in either vector (spot elevation and contour line) or raster (digital elevation model) formats.

The images to the right are derived from maps generated for the U.S. Department of State as part of a large multi-natural hazards assessment for hundreds of locations around the world. We used historical precipitation data to drive the flood model with 100-, 50-, 25-, and 10-year maximum 24-hour precipitation events to derive the corresponding 100-, 50-, 25-, and 10-year floods.