Improved Method of Flood Routing

The standard method of flood routing is modified to make more reliable use of basic river data and to compensate for both sytematic and abrupt changes in river regimen in a complex river system with several interacting branches. It is shown that it is not necessary to find the absolute magnitude of the storage, but only the rate of change of storage per foot of stage. A simple means for relating incremental storage to both stage and slope is developed. The advantages of optimizing reach length are gained without requiring additional data or lengthy computations. The fundamentals governing the practical requirements of reach length and travel-time are explained in terms of the physical situation. Means for dealing with rating curve changes, loop rating curves, levee crevasses, and backwater effects are examined. Results are compared with model tests to use superfloods which pose more numerous and severe problems regarding levee crevasses, floodway operation, etc., than do observed floods.