Detrital Wash Risk MAP Project

Project: Detrital Wash Risk MAP

Client Name: Mohave County Flood Control District

Key Personnel: Brian Schalk – Project Manager

Project Description: The Detrital Wash HUC-8 watershed is located in the north-west part of Mohave County and includes the communities of White Hills and Dolan Springs. Given the proximities of Las Vegas, NV (approximately 60 miles from White Hills, AZ) and the City of Kingman, AZ (approximately 40 miles from Dolan Springs, AZ), a significant increase in the development of transportation-distribution-related businesses, tourist-related businesses, and bedroom communities serving these metro-areas are anticipated within the watershed. The Detrital Wash Risk MAP Project was conducted to provide jurisdictions and developers new flood risk products prior to significant development, which will allow incorporation of accurate flood risk information in the planning process.

Aerial mapping (LiDAR data), two-dimensional H&H analyses (FLO-2D modeling), flood hazard and risk assessment, FEMA floodplain delineation, and development of non-regulatory flood risk products were completed for the Detrital Wash Risk MAP Project. The project area was approximately 770 square miles in size and required 14 individual FLO-2D models (subdomains). Given that H&H analyses were conducted for the 2-, 5-, 10-, 25-, 50-, 100- and 500-year, 24-hour storm events (a total of 7 model runs per subdomain), a total of 98 FLO-2D model runs were submitted to FEMA and Mohave County. FLO-2D models were developed with grids comprised of elements measuring either 20’x20’ or 60’x60’ (based on level of topographic data detail) for each of the fourteen sub-areas. The number of grid elements per subdomain ranged between 38,000 (five square miles) and 2.2M (31.5 square miles). Approximately 31.5 square miles of Zone A floodplain mapping was conducted. Non-regulatory risk map products included: Areas of Mitigation Interest (AOMI), buildings significantly impacted by 10- and 100-year flooding, and 10-year and 100-year hazard classification using various criterion (FEMA, USBR, and FLO-2D). Areas of Mitigation Interest (AOMI) were identified using a combination of FLO-2D results, field reconnaissance, and drainage complaints obtained from Mohave County for the communities of Dolan Springs and White Hills.