Channel stability assessment in the lower reaches of the Krishna River (India) using multi-temporal satellite data during 1973–2015

The present study examines the extent of erosion and deposition along the banks of the lower reaches of the Krishna River (India) between 1973 and 2015, by analyzing the shifts in the bank lines using Landsat images of the years 1973, 1991 and 2015. The analysis is limited to the river segment downstream of the Nagarjuna Sagar Dam up to the Krishna Delta (318 km). The results indicated that the total area lost between 1973 and 1991 due to bank erosion was 3093 ha, whereas the areal extent was reduced to 1386 ha during 1991–2015. Although the individual river reaches had characteristic bank shifting patterns during the period, most of the reaches shifted their banks without changing the bankfull width of the river. Bank erosion was dominated in most of the study reaches during 1973–1991, compared to deposition, while the pattern was reversed during 1991–2015. The contrasting bank erosion/deposition patterns between 1973-1991 and 1991–2015 might be the reflection of the variations in the pattern of flood events between the periods. The impact of the Nagarjuna Sagar Dam on bank erosion is apparent as a sharp increase in the erosion intensity downstream of the dam. The spatial variability of bank erosion is also a function of regional lithology, with marked variability between the Quaternary sediments and other lithological types.