CWE performed a mudflow hazard analysis for City Ventures/William Lyon Homes as part of the hydrology and hydraulics report for the development of Monrovia Nursery Tracts 66608 and 66609 in the City of Glendora. Current regulations require that all debris produced upstream of the site be controlled via debris basins. However, existing homes, fences, walls, and streets impact delivery of sediment to the proposed tracts.
The City of Glendora asked that a special study be conducted to determine whether the debris basins were being oversized based on actual debris delivery. CWE utilized FLO-2D, along with debris yield and hydrograph data, to develop mudflow hydrographs and route them based on existing and proposed conditions. CWE analyzed debris deposition to determine the required basin sizing for the proposed tracts and assess the hazards associated with debris flow.