San Bernardino County rewrites flood design rules last set in 1983

San Bernardino County: The San Bernardino County Flood Control District is updating its Hydrology Manual, the guide engineers use to design storm drains, flood channels, detention basins, and other flood control infrastructure across the county. The manual dates to 1983 and sets the standard for how both public and private projects study rainfall, drainage, and flood risk.

The revision folds in decades of advances in rainfall science, mapping, and flood modeling, plus new guidance for post-wildfire flooding, sediment, and debris-flow analysis. For developers and their engineers, that's the operative change: it resets the design standard new projects must meet. The updated manual and digital resources are posted on the Public Works site.