Extreme Rainfall for Africa and Other Developing Areas

Abstract

Adequate and reliable records of rainfall depth‐duration‐frequency amounts are often not available. Use of estimates of probabilities from limited data can reduce errors due to either underdesign or overdesign of structures and can reduce damage to irrigation facilities and hydraulic structures from floods and excessive runoff. Estimates of extreme rainfall events may also make possible an increased utilization of rain at the locations where it falls. Methods are presented for estimating rainfall intensities with a minimum of data. Equations are given for use with 20‐yr return period monthly rainfall amounts and with daily rainfall extremes. Depth‐duration and depth‐frequency ratios of extreme rainfall amounts have been found to be remarkably uniform within large and diverse geographical areas. This appears to be true for all of Africa. Large expenditures are being made to improve the collection of hydrologic and meteorologic data in the Sahel of Africa. Known ratios and relationships presented herein can improve the use of the existing long records and of data currently being collected. Greater emphasis on training in the use of the climatic data base is now available, and the need to be improved is recommended.