High-Frequency Rainfall-Runoff Modeling for Dam Safety Decision-Making

Dam safety hydrological analyses frequently focus on large, infrequent storm events (500-year event to the probable maximum flood). However, more frequent storms, ranging from 5- to 100-year events, play an important role in risk-based decision-making. For example, it is critical that the impact of higher frequency storms be considered when implementing a reservoir operational restriction. Construction projects also require analysis of frequent storm events. High-frequency storm models are an important tool to verify an extreme storm model.
In conjunction with Hydrometrics, Montana Department of Natural Resources and Conservation (DNRC) Dam Safety Program has developed a procedure and guidance manual to model the effects of frequent storms that can be used by regulators or dam owners for risk-based decision-making. The manual provides suggestions for selecting baseflow values, loss parameters, and tips for verification of a rainfall-runoff model. Depending on the basin size and other complexities, the resulting model is reasonably quick to develop and can inform decision-making or further analyses.