Utilizing HEC HMS for flash flood predictions in semi-arid area: a case study in Devil Canyon, a head watershed of Santa Ana River Basin in CA
Mentor:Helen Jung, Assistant Professor of Civil Engineering, California Baptist Univeristy
Accurate flashing flood prediction is crucial in the region due to the urban areas expanding into the downstream of the mountainous area. The flash flood in this zone carries large amounts of debris which adds to the increased runoff. For this particular study, we used the HEC-HMS model to analyze the behavior of the Devil Canyon watershed from the year 1997 to the year 2006. The HEC-HMS model was developed by the US Army Corps of Engineers for a better analysis and understanding of the hydrologic response and currently being used intensively in flood hydrology. Devil Canyon watershed is located in the San Bernardino Mountains of Southern California and has an area of about 5.5 square miles. The region has a semi-arid climate and most of the precipitation is in the winter (November to March) with 70cm of precipitation per year. The annual precipitation varies heavily with the years and from event to event. The area experiences flash floods due to its geologic and land cover conditions with largely varying rainfall intensity. Our initial findings using the readily available precipitation and runoff data from San Bernardino Flood Control District show that the most of calibrated physical parameters of the watershed during average antecedent condition are not accurate under the dry antecedent condition and few of the major parameters to calculate lag time go beyond the possible physical range. Our work adds to other findings of the case studies in semi-arid area to improve the hydrology predictions. It also demonstrates further investigations of the model’s capability to provide reliable prediction for flash floods.