Dam Safety Incident Report: Benson Creek Rainfall-Runoff Model Results

On the evening of Thursday, August 21, 2014, a rainstorm hit the recently-burned Benson Creek watershed causing considerable flood damage. As described in a previous report in this series, a computerized rainfall-runoff model was compiled to estimate what happened at each of the Wenner Lakes dams during this event.

This report presents a detailed analysis of runoff volumes and peak flows at various locations in the Benson Creek watershed; dam overtopping at the Chalfa and Rabel dams; spillway erosion at the Hawkins Dam that drained the lake; and estimated flood depths in lower Finley Canyon and in lower Benson Creek.

This analysis is limited by the clean-water calculations of the computer model. The effects of debris flows (mudslides) that occurred throughout the watershed are outside the scope of this report.