Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br /> Table II <br /> Obsened "5. Reproduced Flood Peak Flows (cfs) <br /> Septemher 1970 Rainflood Event <br />upper mainstem Dolores Rinr below Rico and Dolores Rinr at Dolores Gage <br /> Peak ds) ~fa....imum 71-hour <br />Location Obser....ed Reproduced Percent ObsCTved Reproduced Percent <br />DitTerence Difference <br />Rico gage 1,930 1.929 0.05% 670. 559 16.6% <br />DolorcsJ'!:a~c 5190 5,143 1.0% \,677"' 1802 8.3% <br />.. Maximum 72-hour is midniJ!ht to midnil!ht data <br /> <br />7. '\Iodelillg the I % Flood Ennt <br />The 1 % chance cxcccdcnce flood event at the Dolores River at Dolores gage is the result of a <br /> <br />general rainstonn on the watershed. This subject is discussed further in Section 8, Flow <br /> <br />Frcquency Analysis. Section 7 includes a discussion of the development of the 1% challee <br /> <br />general rain and the HMS basin parameters used to develop the 1% chance llood hydrograph at <br /> <br />the Dolores gage. <br /> <br />7.1 Previous Storm Modeling. A 2-day Standard projcct Slonn (SPS) was developed in <br />1976 for the HEC~1 rainfal14runoO"computer model. The hourly distribution was based on the <br /> <br />distribution paltcms at the Pleasant View, Silverton. and Durango recording precipitation gages <br /> <br />for the September 1970 stonn <Appendix A Table 5 and Reference 4-c.) A 1% chance rainstonn <br /> <br />was not developed for Ihc 1976 study. <br /> <br />7.2 1% Chance Precipitalion Data. 1% point precipitalion depths for the upper Dolores <br /> <br />River watershed were obtained from Ihc NOAA AlIas 2 web page t'Or the 1-. 2-, 34, 6.0 12. and <br /> <br />24.hollr durations. See Plate II for the 24-hour prccipitation amounts on the basin. Thcse <br /> <br />precipitalion amounts were devcloped in 1973 and have not becn revised yet l'Or the state of <br /> <br />Colorado. The 24-hour precipitation amount is the maximum duration available from NOAA <br /> <br />Atlas 2. A 24day general stann was necded for the 1% rainllood; a relationship between the 1% <br /> <br />24- and 48-hour durations for the upper Dolorcs watcrshed was developed based on a similar <br /> <br />24 <br />