Abstract

Erosion Index is one of the important parameters in estimating soil loss from the Universal Soil Loss Equation of Wischmeier. For this, monthly, seasonal and annual Erosion Index (E1) values of 18 stations in Tamil Nadu were computed for assessing the rainfall erosivity for various stations and preparing the Iso-erodent map of Tamil Nadu. Annual erosion index values are shared by southwest (June - September) and northeast (October-December) monsoon rains in Tamil Nadu. Iso-erodent values for 65 stations were (computed using relationship between mean annual/seasonal (June - September and October - December) rainfall and respective erosion index values. Iso-erodent maps for Tamil Nadu for annual and seasonal (June - September and October December) periods are shown. Annual El values ranges from 299 at Tuticorin to 835 at Nagapatinam. The seasonal (June - September) E1 ranges from 16 at Pamban to 423 at Tirupattur while northeast monsoon El's ranges from 58 at Karur to 555 at Nagapatinam. Variation in El reflects the diversity of rainfall erosion potential in the State. Distribution curves expressing average values are given for 18 stations. Values of Erosion Index for return periods of 2, 5 and 10 years are indicated to assist in assessing soil loss with 20, 20 and 50% probability

Keywords: Rainfall erosion, Iso-erodent value. Erodibility, Erosion Index (El), El distribution curve