Calibrating HEC (Hydrologic Engineering Center) in a Shallow Ice-Covered River

摘要

The HEC-2 computer model was recently modified to accept input for a floating ice cover. Several techniques were evaluated in calibrating the model versus the measured field data for a steep, shallow river. The ice cover thicknesses, as expected, was the dominant parameter affecting the water levels and not the Manning's roughness coefficient of the ice cover. Excellent field data on ice cover thicknesses, water levels and flow discharges were available for calibration. The relatively shallow depths of less than 6 ft and ice covers of up to 3-ft thick created special problems in matching the water levels. The actual ice cover thickness measured in the field should be used as a guide for ice thickness input to the model for shallow streams. The transition of ice cover thickness from are section to the next in the model is extremely critical, otherwise there will be excessive head losses. Several methods for interpolating the ice thickness between the measured sections were attempted in trying to simulate the freeze-up, and ineffective flow areas were blocked off as well. The latter provided the most realistic simulation of flow velocities beneath the ice cover.