Estimating Flood Impacts: A Status Report
Presented at Coasts and Ports 2015 Conference
Policy makers face a range of options to improve flood protection, including physical barriers, improved water network management, relocation, and environmental improvements such as marshland and barrier restoration. Determining the best protection option(s) requires estimates of costs and effectiveness and an estimate of the flood damages that would be avoided.
Efforts to obtain this information have increased over the past decade as concerns regarding potential sea level rise related to climate change have grown. Recent large scale flooding events such as Hurricane Sandy have also prompted greater attention. In the United States, the Army Corps of Engineers developed the HAZUS model to address both property and contents damage from flooding. The model, managed and distributed by the Federal Emergency Management Administration, is capable of translating flood characteristics such as flood extent, depth, and duration. California’s Department of Water Resources, for example, used the model to estimate potential flood damage in all 58 counties (California Flood Future 2013). More recently, the California Coastal Commission sponsored a study to compare investment in marshland restoration in the San Francisco Bay area to the value of expected flood damage avoided using HAZUS (SF Bay Area Economic Institute, URS, and the Brattle Group, 2015).
HAZUS does not tell the whole story on damages, however. While it covers property losses it does not capture other costs such as infrastructure damage (bridges, highways, electricity network facilities (substations, power lines, etc.)) and agricultural losses. Fortunately, there are well developed methods of quantifying these losses as well. Flood maps can also provide the basis for determining infrastructure repair costs, and whether and to what extent transportation networks (air, rail, highway) will be out of service because of flood waters. There is a well-developed literature on costs associated with travel delay and utility service interruptions.
In sum, methods are available to make reasoned estimates of flood damages necessary to make informed flood management decisions.
