Areal PMP distribution of one‐day to three‐day duration over India

Abstract

There is a need to assess the areal depth of the probable maximum precipitation (PMP) over specified catchment areas for the safe construction of dam spillways. The large number of dams in India, coupled with their risk of failure, makes this need imperative both for the maximum use of water resources and for public safety. On the basis of rainfall data for the heaviest storms that occurred in different parts of India during the period 1880–1983, improved estimates of one‐, two‐, and three‐day point PMP for India have been made. In this paper the distribution of areal PMP over specified catchment sizes is provided for the first time. The areal reduction factors (ARF) were based on envelope curves of major storms to give the ARF for areas of 10–20,000 km2 . These factors were found to vary from 1.0 to 0.41, though there was no real difference between durations of rainfall. These values of ARF were then multiplied by values of one‐ to three‐day PMP. The resulting maps allow a broad description of the spatial distribution of areal PMP and also provide a rapid and consistent estimate of the probable maximum flood (PMF) from the PMP. For 500 km2 the areal PMP varies from 40 to 120 cm for one‐day duration; from 70 to 200 cm for twoday duration; and from 75 to 270 cm for three‐day duration. The pattern of PMP is consistent with the geography and available moisture. Copyright © 2002 Royal Meteorological Society.

Review of methods for deriving areal reduction factors

“…Other authors do not find much variation in ARF with the duration of rainfall, probably because they are not studying as wide a range of different durations as presented in the Flood Studies Report (which lists durations from 1 minute to 25 days), and/or are considering comparatively long durations. Clark and Rakhecha (2002) investigated heavy rainfalls of one to three days' duration in India for areas up to 20,000km 2 , and did not find any real difference in ARFs between these durations. Huff (1995) studied shorter durations, between 3 and 24 hours, in the midwest of the United States, and came to the same conclusion.…”

An improved moisture and wind maximization method for probable maximum precipitation estimation and its application to a small catchment in China

“…The idea of substituting points (stations) for areas (catchments) is applied to small catchments; therefore, a point PMP is studied without adjusting the basin shape in our case. However, this approach will work when calculating areal PMPs for large basins, and the isohyet of the transposition area needs to be transposed to the study basin to derive local PMPs (Rakhecha and Clark, ; Clark and Rakhecha, ). Moisture adjustment for relocation …”

Enveloping Curves for the Highest Floods of River basins in India

“…Occurrence of the same type of rainstorms. [10][11][12] Apparently, factors that are responsible in setting meteorological homogeneous regions involve a detailed study of the climatology of spatial distribution of severe rainstorms. Therefore, the spatial distribution and climatological characteristics of severe rainstorms offer much promise in the determination of broad meteorologically homogeneous regions.…”

“…Flood discharges in Indian rivers at various gauging sites are available since about 1950 in numerous scientific papers and reports. [7][8][9][10][11] By pooling together all the information obtained from various publications and reports, the largest flood discharges at sites on major rivers of the three different homogeneous meteorological regions are listed in Table 3. The largest flood discharges on record of rivers in the regions east of 80 0 E and north of 18 0 N, west of 80 0 E and north of 18 0 N and south of 18 0 N range between 1170 and 73,900m 3 /s, 1177 and 69,400 m 3 /s and 13450 and 78,800m 3 /s respectively.…”