CRMP AppendixA Flood Hazard Data Development

<p>This document provides a technical overview of the data and methods used to develop flood hazard data for Phase II of the Virginia Coastal Resilience Master Plan (CRMP). Phase I of the CRMP included only coastal flood hazard data (Dewberry, 2022). Phase II expands the flood hazards to also include pluvial and fluvial hazards. DCR developed robust multi frequency pluvial data in response to stakeholder feedback and priorities from Phase I. Over 280 thousand simulations were completed to provide a wide range of existing and future rainfall conditions for the CRMP study area. Several derivative products were created from these simulations to enable use for the CRMP Phase II Impact Assessment.&nbsp;</p><p>Fluvial data were represented by the Federal Emergency Management Agency (FEMA) Special Flood Hazard Areas (SFHA). Combined representations of the three flood hazards were also developed to understand the spatial extent of each hazard, where compound flooding exists, and what hazards dominate for major flooding.&nbsp;</p><p>Additional changes were made to how the data are represented in terms of planning scenarios to accommodate the additional hazard data and better reflect uncertainty in future climate scenarios. An overview of these aspects is provided in the following text.</p>