Application of hydrological indices for erosion hazard mapping using Spatial Analyst tool

Hydrological indices provide excellent input to geographic information systems for the successful mapping of erosion-prone areas. In this research, a digital elevation model was processed and analyzed to obtain the necessary hydrological indices necessary for erosion modeling. The indices (such as sediment transport index, compound topography index, and stream power index) along with other themes (Like Slope gradient, curvature, distance to channels, and channel density) were overlaid using the "Weighted Sum" overlay tool in the geographic information system. The results showed that 33.14 km² of the test watershed (sub-basin of Abay, Ethiopia) falls in very high/severe erosion zone and needs immediate conservation measures. A total of 98.26 km², 153.40 km², and 263.17 km² fall in high-, moderate-, and low-erosion hazard zones, respectively. Therefore, the primary and secondary derivatives of the digital elevation model along with morphometric parameters coupled with a Spatial Analyst tool proves to be a powerful integrated approach in demarcating erosion vulnerable zones and could be applied at regional and continental scale for proper watershed management.