Development Of Rainfall Erosivity Map For Nigeria

Rainfall data spanning about a period o 36 years, were used to compute rainfall erosivity indices for some selected stations in Nigeria. About 38 locations were selected, cutting across all the five agro-ecological zones of Nigeria. The Fournier index, which is defined as quotient of the squared sum of rainfall of wettest month of the year to the annual rainfall was used. Values of rainfall erosivity indices ranged from 26.0mm at yandev in the south –eastern of Nigeria, to 106.7 mm at Yelwa in the north-eastern part of the country. The indices were used to develop a rainfall erosivity map or Nigeria. The map reveals that Nigeria may be broadly divided into five major erosion risk zones. The south-western part is generally in the low erosion zone, with the exception of the coastal portion of Lagos, Ondo, Edo and Delta states. The south-east and central portions are generally in the moderate to severe erosion rise zone, while the extreme north-west and north-eastern part are in the severe to extremely sever risk zone. KEY WORDS: Erosivity, Rainfall, Erosion, Fournier-Index. Global Journal of Pure and Applied Sciences Vol.11(2) 2005: 253-25