Since 2000, the Nagavali River has gained attention due to the Indian government’s plans for ten hydro-power projects within its basin. Flowing through a structurally complex longitudinal valley between eastern and western ridges in Orissa and Andhra Pradesh before emptying into the Bay of Bengal, the Nagavali River is prone to flooding. In this chapter, out of those ten project sites risk assessments have focused on two sites: Hathipahar in Rayagada, Orissa, and Thotapalli in Srikakulam District, Andhra Pradesh. Hathipahar, situated on a piedmont slope of Khandelite-granite, and Thotapalli, on a rolling plain, faced different fates in past flood events. In July 2006, torrential rains and flash floods caused the collapse of an under-construction dam at Hathipahar, resulting in significant channel shifting (about 550 m), erosion, and soil loss. Conversely, Thotapalli, unaffected by this flood, saw its dam completed in 2015. However, subsequent floods in 2014, 2017, and 2020 caused the reservoir at Thotapalli to expand from 2.1 to 9.16 km2, with the river’s upstream width also increasing. The current research evaluates the vulnerability of these two sites to fluvial hazards and assesses the risks of future hydro-power projects. It involves analyzing general slope, land use changes, channel width-depth variations, and sediment grain size. Socio-economic vulnerability is assessed through damage estimates and hazard thresholds. Susceptibility analysis uses 120 years of rainfall data, lithological studies, SOI topographical maps, Google Earth images, and SRTM DEM. Field surveys support the creation of elevation models, sediment analysis, and facies assessment.
