• SHAIK MAHAMMAD IBRAHEEM
• VEMU SREENIVASULU

Reliable estimation of the Probable Maximum Flood (PMF) is essential for verifying the flood-handling capacity of high-hazard hydraulic structures such as spillways and flood-control dams. This paper presents a GIS-based estimation of the one-day design storm (PMP) and the corresponding PMF for the catchment of the Paidipalem Reservoir, a balancing reservoir of the Gandikota Lift Irrigation Scheme located in Simhadripuram mandal of YSR Kadapa district, Andhra Pradesh. The catchment, delineated from SRTM DEM data using ArcGIS, has an area of 12.141 sq.km, a longest flow path of 6.537 km, a centroidal flow path of 4.357 km and a catchment slope of 7.087 m/km. A Synthetic Unit Hydrograph (SUH) derived from the Central Water Commission (CWC) regional relationships for Krishna and Pennar Sub-zone 3(h) gave a peak discharge of 9.89 cumecs, a time to peak of 1.5 hours and a time base of 10 hours. The storm of 6 October 1994 centred at Atmakur (464 mm) was transposed to the catchment, giving an area-weighted rainfall of 400 mm and, with the grid-point Transposition Adjustment Factor, a Standard Project Storm depth of 389.0 mm, which after clock-hour correction yielded a design one-day PMP of 439.0 mm. This depth was distributed into two 12-hour bells (69.20% and 30.80%), reduced by a design loss rate of 0.10 cm/hr, arranged in the critical B2-B1 sequence and convolved with the SUH ordinates. After adding a base flow of 0.61 cumecs, the PMF was found to be 123.09 cumecs (4,346.99 cusecs) at the 21st hour, which is lower than the original design flood of 169.9 cumecs. The workflow is reproducible and can be transferred to other ungauged catchments of the same sub-zone.

"ESTIMATION OF PROBABLE MAXIMUM FLOOD FOR THE PAIDIPALEM RESERVOIR CATCHMENT", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.13, Issue 10, page no.a273-a280, October-2026, Available :http://www.jetir.org/papers/JETIR2610029.pdf

"ESTIMATION OF PROBABLE MAXIMUM FLOOD FOR THE PAIDIPALEM RESERVOIR CATCHMENT", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.13, Issue 10, page no. ppa273-a280, October-2026, Available at : http://www.jetir.org/papers/JETIR2610029.pdf