Xing Fang
Theodore G. Cleveland
David B. Thompson
William H. Asquith
Luke J. Marzen
Nirajan Dhakal
2011
<div class="NLM_sec NLM_sec_level_1 hlFld-Abstract"><p>The rational method for peak discharge (<span class="equationTd"><span id="MathJax-Element-1-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>Q</mi><mi>p</mi></msub></math>"><span id="MathJax-Span-1" class="math"><span><span id="MathJax-Span-2" class="mrow"><span id="MathJax-Span-3" class="msub"><i><span id="MathJax-Span-4" class="mi">Q</span></i><sub><span id="MathJax-Span-5" class="mi">p</span></sub></span></span></span></span></span></span>) estimation was introduced in the 1880s. Although the rational method is considered simplistic, it remains an effective method for estimating peak discharge for small watersheds. The runoff coefficient (<i><span class="equationTd"><span id="MathJax-Element-2-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mi>C</mi></math>"><span id="MathJax-Span-6" class="math"><span><span id="MathJax-Span-7" class="mrow"><span id="MathJax-Span-8" class="mi">C</span></span></span></span></span></span></i>) is a key parameter for the rational method and can be estimated in various ways. Literature-based<span> </span><i><span class="equationTd"><span id="MathJax-Element-3-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mi>C</mi></math>"><span id="MathJax-Span-9" class="math"><span><span id="MathJax-Span-10" class="mrow"><span id="MathJax-Span-11" class="mi">C</span></span></span></span></span></span></i><span> </span>values (<span class="equationTd"><span id="MathJax-Element-4-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>C</mi><mi>lit</mi></msub></math>"><span id="MathJax-Span-12" class="math"><span><span id="MathJax-Span-13" class="mrow"><span id="MathJax-Span-14" class="msub"><i><span id="MathJax-Span-15" class="mi">C</span></i><span id="MathJax-Span-16" class="mi"><sub>lit</sub></span></span></span></span></span></span></span>) are listed for different land-use/land cover (two words, no hyphen) (LULC) conditions in various design manuals and textbooks; however, these<span> <span class="equationTd"><span id="MathJax-Element-4-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>C</mi><mi>lit</mi></msub></math>"><span id="MathJax-Span-12" class="math"><span id="MathJax-Span-13" class="mrow"><span id="MathJax-Span-14" class="msub"><i><span id="MathJax-Span-15" class="mi">C</span></i><span id="MathJax-Span-16" class="mi"><sub>lit</sub></span></span></span></span></span></span></span><span> </span>values were developed with little basis on observed rainfall and runoff data. In this paper,<span> <span class="equationTd"><span id="MathJax-Element-4-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>C</mi><mi>lit</mi></msub></math>"><span id="MathJax-Span-12" class="math"><span id="MathJax-Span-13" class="mrow"><span id="MathJax-Span-14" class="msub"><i><span id="MathJax-Span-15" class="mi">C</span></i><span id="MathJax-Span-16" class="mi"><sub>lit</sub></span></span></span></span></span></span></span><span> </span>values were derived for 90 watersheds in Texas by using LULC data for 1992 and 2001; the<span> <span class="equationTd"><span id="MathJax-Element-4-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>C</mi><mi>lit</mi></msub></math>"><span id="MathJax-Span-12" class="math"><span id="MathJax-Span-13" class="mrow"><span id="MathJax-Span-14" class="msub"><i><span id="MathJax-Span-15" class="mi">C</span></i><span id="MathJax-Span-16" class="mi"><sub>lit</sub></span></span></span></span></span></span></span><span> </span>values derived from the two data sets were essentially the same. Also for this study, volumetric runoff coefficients (<span class="equationTd"><span id="MathJax-Element-8-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>C</mi><mi>v</mi></msub></math>"><span id="MathJax-Span-32" class="math"><span><span id="MathJax-Span-33" class="mrow"><span id="MathJax-Span-34" class="msub"><i><span id="MathJax-Span-35" class="mi">C</span></i><sub><span id="MathJax-Span-36" class="mi">v</span></sub></span></span></span></span></span></span>) were estimated by using observed rainfall and runoff depths from more than 1,600 events observed in the watersheds. Watershed-median and watershed-average<span> <span class="equationTd"><span id="MathJax-Element-8-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>C</mi><mi>v</mi></msub></math>"><span id="MathJax-Span-32" class="math"><span id="MathJax-Span-33" class="mrow"><span id="MathJax-Span-34" class="msub"><i><span id="MathJax-Span-35" class="mi">C</span></i><sub><span id="MathJax-Span-36" class="mi">v</span></sub></span></span></span></span></span></span><span> </span>values were computed, and both are consistent with data from the National Urban Runoff Program. In addition,<span> <span class="equationTd"><span id="MathJax-Element-8-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>C</mi><mi>v</mi></msub></math>"><span id="MathJax-Span-32" class="math"><span id="MathJax-Span-33" class="mrow"><span id="MathJax-Span-34" class="msub"><i><span id="MathJax-Span-35" class="mi">C</span></i><sub><span id="MathJax-Span-36" class="mi">v</span></sub></span></span></span></span></span></span><span> </span>values were estimated by using rank-ordered pairs of rainfall and runoff depths (i.e., frequency matching). As anticipated,<span> </span><i><span class="equationTd"><span id="MathJax-Element-11-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mi>C</mi></math>"><span id="MathJax-Span-47" class="math"><span><span id="MathJax-Span-48" class="mrow"><span id="MathJax-Span-49" class="mi">C</span></span></span></span></span></span></i><span> </span>values derived by all three methods (literature based, event totals, and frequency matching) consistently had larger values for developed watersheds than for undeveloped watersheds. Two regression equations of<span> <span class="equationTd"><span id="MathJax-Element-8-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>C</mi><mi>v</mi></msub></math>"><span id="MathJax-Span-32" class="math"><span id="MathJax-Span-33" class="mrow"><span id="MathJax-Span-34" class="msub"><i><span id="MathJax-Span-35" class="mi">C</span></i><sub><span id="MathJax-Span-36" class="mi">v</span></sub></span></span></span></span></span></span><span> </span>versus percent impervious area were developed and combined into a single equation that can be used to rapidly estimate<span> <span class="equationTd"><span id="MathJax-Element-8-Frame" class="MathJax" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><msub><mi>C</mi><mi>v</mi></msub></math>"><span id="MathJax-Span-32" class="math"><span id="MathJax-Span-33" class="mrow"><span id="MathJax-Span-34" class="msub"><i><span id="MathJax-Span-35" class="mi">C</span></i><sub><span id="MathJax-Span-36" class="mi">v</span></sub></span></span></span></span></span></span><span> </span>values for similar Texas watersheds.</p></div>
application/pdf
10.1061/(ASCE)IR.1943-4774.0000368
en
American Society of Civil Engineers
Estimation of volumetric runoff coefficients for Texas watersheds using land-use and rainfall-runoff data
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