Rasyonel Yöntemin Rasyonel Olmayışı ve İyileştirilmesi

Rational Method Irrationality with Rectification

Rational method (RM) is the simplest approach for peak discharge calculation, but it has many simplifying and unrealistic assumptions, which cause biased results in many applications. Among the most important drawbacks are its applicability restriction to small areas, but it is also used without much care even for large, flat and horizontal areas, even though drainage basins might have significant slopes and rough topography. In the RM the rainfall intensity is taken as constant during the storm rainfall duration and over the drainage area coverage. In this paper, first the RM irrationalities are explained and then a modified formulation is proposed by reconsidering geomorphologic and rainfall features. Nonlinear relationships, in the forms of double-logarithmic functions, of peak discharge with drainage area and slope are incorporated in the new formulation. Its application is achieved for a set of drainage sub-basins from the Kingdom of Saudi Arabia.

Keywords:

Drainage area, peak discharge, rainfall intensity, rational method slopes,

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Al-Zahrani, M. K., Al-Harthi, S. G., Hawsawi, H. M., Al -Ammawi, F. A., Theban, M. S., Khiyami, H. A., Bulkhi, A., Şen, Z. (2007). Potential Flood Hazard in Wadi Baish Southwest, Saudi Arabia. Saudi Geological Survey Confidential Report, 216 pp.
Bayazıt, M., Önöz, B. (2008). Taşkın ve kuraklık hidrolojisi, Nobel Yayınevi, ISBN: 978-605-395-142-1, İstanbul, Ekim.
Chow, V., Maidment, D., Mays, L. (1988). Applied hydrology: McGraw-Hill, New York, 572 P.
Costa, J.E. (1987). A comparison of the largest rainfall-runoff floods in the United States with those of the People’s Republic of China and the world in W.H. Kirby, S.Q. Hua and L.R. Beard, eds, Analysis of extraordinary flood events: Journal of Hydrology, v. 96, p. 101–115.
Hjelmfelt, Jr. A. T. (1991). Investigation of curve number procedure. Journal of Hydrologic Engineering, ASCE 117(6): 725–737.
Kirpich, Z. P. (1940). Time of concentration of small agricultural watersheds. Civil Engineering 10 (6), 362. The original source for the Kirpich equation.
Kadioglu M, Şen Z. (2001). Monthly precipitation–runoff polygons and mean runoff coefficients. Hydrological Sciences Journal 46(1): 3–11.
Linsley, R.K. (1982). Rainfall - runoff models - an overview. In Proceedings of the International Symposium on Rainfall–Runoff Relationship, Singh VP (ed.). Water Resources Publications: Littleton, CO.
Maidment, D.R. (1993). Handbook of Hydrology. McGraw-Hill, Inc., New York.
Omolayo, A. S. (1993). On the transformation of areal reduction factors for rainfall frequency estimations. Journal of Hydrology, 145, 191-205.
Pilgrim, D. H., Cordery, I. (1993). Flood Runoff. Handbook of Hydrology, Maidment DR (ed.). McGraw-Hill: New York; 9.1–9.42.
Ponce, V. M., Hawkins, R. H. (1996). Runoff curve number: has it reached maturity? Journal of Hydrologic Engineering, ASCE 1(1): 11–19.
Sirdaş, S., Şen, Z. (2007). Determination of Flash Floods in Western Arabian Peninsula Journal of Hydrologic Engineering , ASCE, Vol. 12 , No. 6, 676-681.
Şen, Z., Al-Suba’i K. (2002). Hydrological considerations for dam siting in arid regions: Saudi Arabia study. Hydrological Sciences Journal, 47(2) 173-186.
Şen, Z. (2008). Wadi Hydrology. Taylor and Francis Group, CRC Press, Boca Raton, 345 pp.
Şen, Z., (2010). Fuzzy Logic and Hydrological Modeling. Taylor and Francis Group, CRC Press Publishers, 340.
Soil Conservation Service (SCS). (1971). National Engineering Handbook, Section 4: Hydrology. USDA: Springfield, VA
Soil Conservation Service (SCS). (1986). Urban Hydrology for Small Watersheds, Technical Report 55. USDA: Springfield, VA.