Safety of Dams Flood and Earthquake Criteria (1985) / Chapter Skim
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Appendix C: Probable Maximum Precipitation (PMP) Estimates
Appendix C: Probable Maximum Precipitation (PMP) Estimates
Pages 211-226
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From page 211... ...
A joint effort of the Corps of Engineers and the Weather Service has provided and kept current a looseleaf publication that contains data on the most extreme observed areal storm rainfalls (U.S. Army Corps of Engineers, 1945~.
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From page 212... ...
A more generalized transposition procedure has been used for tropical storm rainfalls along the Gulf and east coasts of the United States (Schreiner and Riedel, 1978~. This gives adjustments to rain depths based on the decrease with distance inland from the coast observed in the major tropical storms.
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From page 213... ...
Such envelopment takes into account the strong possibility that we have not experienced equally extreme rainfall-producing parameters in the observed storms, etc., for all area sizes and durations. Another envelopment step is introduced by utilizing smooth lines and gradients for PMP estimates when making generalized PMP estimates for a region.
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From page 214... ...
. GENERALIZED PMP CHARTS It has been found that more reliable and consistent PMP estimates result from studies giving mapped values for a region.
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From page 215... ...
Detailed instructions and recommendations for application of PMP for the United States east of the 105th meridian have been published (Hansen et al., 1982~. This report covers the spatial distributions within any specified drainage and the sequence of incremental 6-hourly rain depths in the PMP storm.
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From page 216... ...
A E ~ _ Ct ~ 0 0 CD _ ,~ ~ ~ ~ ~ oO 0 — 0 _ ~ ~ CD ~' ~ ~ ~ or w 3 y ~ A ~ ~ a 5 O Co ~ 0 Co ~ ~ 0 _ C~ o =4 ~ d4 =4 ~ U' O ~ O O ~ O O O O ~Z ZZ Z Z Z Z
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From page 217... ...
~ (~ ~£ ~5 ,~ o._ ~ ~ ~ =-y 1/ ~~: ~ ~ ~ c , ~ ~ _ E ~ E _ ~ ~ ~ ~ ~ ' Cat d ~ ~ Cot ~ ~ ~ ~ us o o o o o ~ ~ = Z Z Z ~ Z z ~ ==
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From page 219... ...
Sequences of the 6-hour PMP increments (that is, in what order they occur relative to their magnitude) vary widely in major storms.
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From page 220... ...
PMP. Published studies that include seasonal variation for areas in the United States are listed in Table C-1.
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From page 221... ...
221 EVALUATION OF PMP It is assumed in a study of PMP, that there is no climatic trend in the meteorologic parameters that would increase or decrease the estimates in the foreseeable future. PMP for the United States is based largely on the greatest recorded rainstorms that have occurred mainly since about 1860 (a few on record prior to this year)
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From page 222... ...
, eastern United States. Source: Riedel and Schreiner (1980~.
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From page 223... ...
, western United States. Source: Riedel and Schreiner (1980)
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From page 225... ...
Using many series of station maximum annual 24-hour rainfall events, mostly in the United States but also some in other countries, the greatest value found of Km to obtain Xm was 15. Use of this value was suggested to compute statistical PMP.
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From page 226... ...
Here the variable K factor was used to compute the statistical PMP for 98 stations. Only 2 of the 98 statistical PMP values exceeded the PMP of the report.
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