Estimating the Hydrological Influence of Maryland State Dams Using GIS and the HEC-1 Model

Abstract

This study develops a quantitative relation defining the extent of influence that a dam imposes on annual peak streamflow, and employs the developed relation to retain the use of some USGS gauges in the state of Maryland for regional flood frequency analysis (FFA). Stage-storage–discharge curves for 34 dams in Maryland were provided by the Maryland Department of Environment Division of Dam Safety. Each watershed/dam system was analyzed using HEC-1. The results were used to form two linear equations that calculate the influence distance, or the downstream reach length affected by each dam, for a 5 and 10% level of regulation. The level of regulation is the measured amount, in percent, that the peak flow in a stream is influenced by the presence of the structure. When the influence distance predictor equations were applied throughout the state of Maryland at the 10% regulation level, we found that 32 of the