Factors influencing runoff during the flood of December, 1937, in northern California

Abstract

Engineers and hydrologists engaged on flood‐problems throughout much of the United States east of the Rocky Mountains must deal to a considerable extent with wide‐spread storms covering thousands of square miles. The gradations of meteorologic conditions as regard both area and time are relatively homogeneous during such storm‐events and are affected but moderately by orographical influences. Under such conditions similar storm‐characteristics prevail over vast areas. True, precipitation decreases toward the boundaries of such major storm‐areas, and locally precipitation‐rates may greatly exceed the average. Often, however, drainage‐basin after drainage‐basin will yield comparable depths of flood‐runoff. The storms of March, 1936, which resulted in the simultaneous occurrence of floods throughout all of the northeastern part of the United States from Ohio and Virginia to Maine and the storm of January, 1937, which embraced all of the 200,000 square miles comprising the Ohio River drainage are typical of major Eastern disturbances. The storm of December, 1937, in the Sacramento and San Joaquin valleys is used herein to illustrate what may be called a typical major California disturbance, and it is this storm and resulting flood that I wish to consider in some detail and also to make such comparisons and contrasts with Eastern floods as seem to be of general interest.