Physically-based modeling for improved flood prediction in the Elbow River watershed
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AbstractThis research focuses on comparing flood forecasting by a lumped model and a physically-based distributed model in southern Alberta. It also includes urbanization impacts on the hydrology, and climate change impacts on hydrology of this area. The lumped model is called Streamflow Synthesis and Reservoir Regulation (SSARR), and the distributed model is PRMS. The SSARR model was developed by USACE, and the PRMS model was developed by USGS. The Elbow River Watershed was chosen as the study area. Five years of data were selected for calibration and verification. The simulation periods are long-term periods from April 1 to August 31 and short-term events with focus on peak flows for 5 days before and after the event. Time step is 3 hourly increments in the SSARR model, and 1 hour for PRMS. The calibrated SSARR model was accepted by Alberta Environment, and will be operated in Elbow river basins this year. The calibrated model is suitable for the Upper basin, the Lower basin and the Whole basin, and for wet, medium and dry years. The calibrated PRMS model was just suitable for the Upper basin because of poor river routing from the upper basin to the lower basin, and for just wet and medium years. By comparing these two models, the SSARR model is better flood forecasting for the Elbow River Watershed. The impact of urbanization on the hydrology of the Elbow River Watershed was simulated by the PRMS model. The peak flows and volumes increase with an increase in impervious area, but the changes of flows and volumes are very small. Times to peak in different years are not affected. As a result, the impact of urbanization in Elbow River Watershed is not big enough on the quantity of hydrology. The impact of climate change on the hydrology of the Elbow River Watershed was simulated by the PRMS and SSARR. The simulated results indicated that the climate change would lead to the significant changes of flows and volumes, and time to peak. By comparing these two models, different results result from different routing. The impact of logging on the hydrology of the Elbow River Watershed was simulated by the PRMS. Clear cutting would give rise to the increase of flows and volumes, and earlier time to peak. Floodplain in the lower reach of the Elbow River was delineated in HEC-RAS and HEC-GeoRAS. The cross-section, water surface profile, rating curve, and x-y-z perspective plots were produced.
Bibliography: p. 161-164