Abstract:
Estimates of probable maximum precipitation (PMP) and corresponding probable maximum flood (PMF) are necessary for
planning, design, and risk assessment of flood control structures whose failure could have catastrophic consequences. For PMP
estimation, multifractal approach (MA) is deemed to be better than conventional approaches, which are based either on statistical
concepts or physical aspects. The MA yields physically meaningful PMP estimates by attempting to capture scale-invariant
multiplicative cascade mechanism inherent in rainfall. This paper attempts to gain insights into the performance of MA by
comparing PMP estimates obtained using the approach with those resulting from the use of two widely used empirical approaches (storm maximization approach (SMA) and Hershfield method (HM)) on two flood-prone river basins (Mahanadi and
Godavari) in India. The results indicate that rainfall data of the two river basins exhibit multifractal properties, and the use of MA
has an advantage over HM and SMA in estimating PMP corresponding to longer durations (>3 days). PMP estimates obtained
using HM are generally lower (higher) than those obtained using SMA for 1-day (higher) duration. PMP maps are prepared for
the two Indian river basins corresponding to 1-day to 5-day durations. Further, PMP estimates obtained based on the PMP maps
are provided for 18 catchments in the Mahanadi basin and 53 catchments in the Godavari river basin.
