Laserfiche WebLink
<br /> <br />I <br />I <br />I <br /> <br />- 9 - <br /> <br />\s~le~~e~-?y the enginee~1and used as a basis for Mr. Mulvey's <br />storm calculations. His reports. in Appendix A. go into detail <br />of the meteorological events that lead up to the creation of <br />a thunderstorm. <br /> <br />I <br />I <br />I <br />I <br /> <br />While Mr. Mulvey's reports define the most probable location and <br />areal extent of the maximum potential storm for each frequency <br />event in the basin. it is possible for flood producing storms of <br />smaller magnitude to occur elsewhere. Runoff was determined from <br />storm events occurring over major tributaries of the Blue River <br />below the "Tarn". Because the summer thunderstorm is of small <br />areal extent. runoff'was assumed to come only from the tributary <br />over which the storm was centered. Adjacent tributaries also <br />contribute runoff. lilt this did not appreciably affect the peak <br />discharge due to shape of the basins. smaller storm intensities <br />and timp of concentration of the individual"basins. Figure 2 <br />summarizes the runoff from a storm occurring over the various <br />tributaries below the Tarn with a base flow from the Tarn of <br />90 cfs. The flow in the Blue River is derived from the tributary <br />runoff plus base flow which gives the highest peak runoff. It <br />was found that. except for the SPF runoff from Swan River. Lehman <br />Gulch runoff was the controlling flow. <br /> <br />I <br />I <br />I <br />I <br />I <br />!I" <br />I <br /> <br />RUNOFF INVESTIGATION <br /> <br />The MIT Catchment Model (MITCAT) was used to derive runoff from <br />synthetic storms for the four flood frequencies. This model is <br />. a general purpose simulation model of a watershed which was de- <br />veloped at the Massachusetts Institute of Technology. The model <br />is formulated in a problem-oriented language with a flexible <br />command structure offering many input/output and computation <br />options. It uses a Kinematic wave function. one of the simplest <br />and most useful approaches available to the hydrologist today. <br /> <br />I <br />I <br />I <br />I <br /> <br />A basin is modeled as a synthesized network of overland flow <br />planes. stream reaches. and reservoirs. By segmenting the basin. <br />the various hydrologic features can be analyzed as they vary at <br />different points in space and time. <br />" <br /> <br />Input requirements for the MITCAT Model include Technical Paper <br />40'precipitation reduced to half-hour intensities. overland "n" <br />values which are used to model runoff prior to flow in the channel. <br />channel "n' values. and trapizoidal channel shapes which are used <br /> <br />I <br /> <br />~ Leonard Rice Consultrng Water Engineers,lnc, <br />