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<br />002J97 <br /> <br />1.4 Historic ~loods <br /> <br />Flooding on the Rio Grande can result from snowmelt runoff, <br />general rains, cloudburst storms, or a combination of those <br />condi tions. The runoff from snowmelt occurs during the period <br />from late May to early July. This is the time of the year that <br />the river is most susceptible to flooding, especially if there <br />are warmer than usual temperatures and the snowmelt is augmented <br />withrain. Runoff from snowmelt is characterized by moderate peak <br />flows, long duration, and large volumes of water. Most of the <br />annual rainfall occurs during the months of July through <br />October. The intensity of rainfall is moderate to high, and the <br />runoff is characterized by high peak flows of short duration with <br />relatively small volumes of water. Following are notable floods <br />of record at various locations: <br /> <br />HISTORIC FLOODS ON THE RIO GRANDE <br /> <br />Date <br />1869 <br />Spring 1884 <br />June 5, 1905 <br />Oct. 5, 1911 <br />June 13, 1921 <br />June 29, 1927 <br />Nay 22, 1948 <br />June 19, 1949 <br />t'Jay 30, 1979 <br />June 9, 1985 <br /> <br />Location <br />Alamosa <br />Alamosa <br />Del Norte <br />Del Norte <br />Del Norte <br />Del Norte <br />Mon'te Vista <br />Monte Vista <br />Del Norte <br />Del Norte <br /> <br />Discharge <br />Cubic Feet/Second <br />Unknown <br />+ 20,000 <br />10,000 <br />18,000 <br />9,630 <br />15,000 <br />7,100 <br />6,650 <br />8,060 <br />9,040 <br /> <br />Of the several recorded floods, all but one occurred during <br />the months of Hay to July. The flood of June 1884, caused <br />primarily by extraordinary snow cover, lasted much longer than <br />the others. The river was at overflow stage at Del Norte from <br />about Nay 24 to June 20. In other years, the flood stage has <br />remained for only a few days. The highest flood since gaging <br />station records have been kept was that of June, 1927; but the <br />flood of 1884, which occurred before any station had been <br />\ established, may have been higher, and the October 1:911 flood was <br />higher at Del Norte. <br />-7 ", ' <br />The flood of October 1911 was caused by widespread heavy <br />rains throughout southwestern Colorado. The flood' of 1927 was <br />caused by a combination of factors: heavy 'snow cover, <br />precipitation in the form of snow, followed immediately by sudden <br />increase in temperature, and rain during the period of maximum <br />snow melting. The flood of May 1979 was caused by melting snow. <br /> <br />1.. <br />, I '1 <br />\ ;'1.\}J' , <br />\f'I\'^ U <br /> <br />-3- <br />