Hydrology of Spillway Design Floods: Large Structures–Limited Data

Procedures for estimating probable maximum floods for large dams in areas with limited hydrologic data are given, primarily for areas outside the United States. The various levels of accuracy required for different phases of investigation are emphasized. The use of envelope and frequency curves for preliminary estimates is examined. Methods of developing probable maximum storms in areas of limited precipitation data are described. The use of world record envelopes of precipitation, isopercental techniques in transposition of storms, and the use of limited local storm data are investigated. Unit hydrograph derivation for areas with limited runoff data is illustrated. Application of U. S. data on precipitation, retention losses, and unit hydrograph derivation is emphasized. Case histories on flood derivation are presented.