Applying Climate Change Models to Risk Assessment and Flood Hazard Scenario Modeling in Snohomish County
Veith, Stephen Glenn
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University of Washington Abstract Applying Climate Change Models to Risk Assessment and Flood Hazard Scenario Modeling in Snohomish County Stephen Glenn Veith Chair of the Supervisory Committee: Assistant Professor Himanshu Grover Department of Urban Design and Planning This thesis analyzes and evaluates the utility of using HAZUS-MH, hazard modeling and loss estimation software used by the United States Federal Emergency Management Agency (FEMA), to estimate future losses from climate change influenced flood events under different greenhouse gas emissions scenarios. Current FEMA flood scenario techniques involve generating probabilities for floods for return intervals of 10, 20, 50, 100 and 500 years. These flood return intervals are typically based on historical record, which does not factor changes in climate into future estimates of risk. However, this thesis has integrated projected future flood return intervals and river discharges from the University of Washington’s Climate Impacts Group. This is done so that future flood return intervals and river discharges, which show an increase in flood frequency and magnitude in the future due to climate change, can be modeled. When climate change is factored into flood modeling, the areas of greatest future risk in a community can be identified. The particular community used as a case study in this thesis is the City of Sultan and surrounding Urban Growth Area. To quantify the difference in exposure and risk, the 5 different scenarios used in this thesis are calculated at 100 year flood return interval periods: the first scenario as the FEMA baseline with no climate data added, the other scenarios use climate projections for 2040 and 2080. These scenarios use existing data incorporated into HAZUS-MH to create river hydrology, depth grids and loss-estimates to building stock and social capital in the present day and in the future using population growth projections. The risk and exposure of each scenario is presented and compared, which ultimately leads to estimates that the designated Sultan Urban Growth Area will incur increased risk and loss in the future as floods become more frequent due to climate change. These results show that current 100 year floodplain boundaries may not adequately inform communities about the potential flood risk in the future due to climate change, and should change how urban planners decide to prepare communities for flooding hazards as the effects of climate change influence river systems.
- Urban planning