The 1948 flood of the Columbia river an analysis of its cause and its importance in operation planning

The 1948 flood on the Columbia River has significant implications to the Corps of Engineers in the formulation of flood control criteria for reservoirs in the Columbia basin, because it had a large runoff forecast error - in which spring runoff was significantly greater than predicted by snow and winter precipitation indices. An analysis was made of the hydrometeorology of this event, including the magnitude of the snowpack, magnitude and distribution of spring rainfall, and temperatures. Using the SSAARR hydrologic model these factors were simulated in various combinations and compared with other years. The conclusions were that no single factor that produced the flood was extremely rare, but their combination was relatively unique. The event could be considered more rare than its nominal recurrence interval of approximately 50 years computed from streamflow records.