Over the past few years, the National Academy of Sciences, the Technical Mapping Advisory Council, and flood insurance legislation have all recommended or mandated that the Federal Emergency Management Agency (FEMA) modernize the process by which flood risk is calculated and communicated, and that the data produced must be able to support evolving and expanding program needs. As more and more flood events continue to occur that affect those living outside the 100-year floodplain, and as the Risk Mapping, Assessment, and Planning (Risk MAP) program continues advancing towards structure-level risk assessment, mitigation, and insurance ratings, it is critical that inherent uncertainties in hydrologic and hydraulic modeling be taken into account, and a larger range of possible flood scenarios be considered.
AECOM is supporting FEMA in developing a novel approach to calculating flood risk. Uncertainty in hydrology (streamflow and rainfall), curve number, and Manning’s n-values are all considered in the flood modeling process through a Monte Carlo simulation approach. The likelihood of levees breaching or overtopping can also be considered. Thousands of model scenarios are run through two-dimensional hydraulic models in a cloud computing environment to calculate flood elevations and extents. The results are appropriately weighted and applied to generate flood probability heat maps, detailed water surface elevation probability distribution curves, flood damage curves, and annualized losses at any structure or location of interest, taking into account uncertainties in structure occupancy or first floor elevation. This presentation is intended to provide an overview of the methodology and model development for this novel approach to calculating flood risk.
Yacoub is a water resources engineer with over seven years of experience. He has performed technical design, planning, and computer modeling on projects related to flooding, dams, reservoirs, levees, water supply systems, stormwater, drainage, watershed management, and stream and environmental restoration.