Flood meteorology, hydrology, and geomorphology of the Upper Godavari River, Western India

Meteorological, hydrological, and geomorphological aspects of large floods on the Upper Godavari River were investigated. Synoptic conditions associated with large floods were analyzed to gain an understanding of flood hydrometeorology in the basin. The study reveals that the southwest summer monsoon dominates rainfall in the Upper Godavari Basin (90% of annual rainfall). Moreover, interannual variability was characterized by increased frequency and magnitude of floods primarily after the 1930s and the majority of large floods were connected with low-pressure systems. Unit discharges (Q(u)) and flash-flood magnitude index (FFMI) were computed to understand the potential for large floods. The high Q(u) (1.13 and 6.00 m3 s(-1) km(-2)) are likely to be effective in terms of geomorphic changes in the channel. The greater FFMI values (0.27 and 0.56) indicate the flashy and variable nature of floods and the possibility of significant geomorphic work. Parameters of flood hydraulics and hydrodynamics were computed to estimate the efficacy of infrequent and large-magnitude floods. The highest values for unit stream power (5909.61 W m(-2)) and bed shear stress (609 N m(-2)) reveal the unusually high capacity of the river to erode and transport coarse sediments. The Froude numbers (>1) confirm extremely erosive supercritical flows. High Reynolds numbers indicate exceedingly turbulent flood discharges, capable of accomplishing a variety of geomorphic activities.