I 



D/SCUSS/ON 



In general, the mountain-valley intensity relationships stated by Brancato (1942) 

 hold true for these data. He stated: 



With regard to variation of thunderstorm rainfall with 

 elevation ... over a long period of time a station 

 located at a lower elevation is likely to experience the 

 most intense thunderstorm. 



Dorroh (1946) also substantiates this hypothesis. However, the maximum expected rain- 

 fall intensities in the aspen-fir type are somewhat lower than those expected at either 

 higher or lower elevations. 



Plant cover destruction resulting in active flood and sediment source areas has 

 occurred prevalently on high-elevation herbaceous sites that lie above the aspen-fir 

 type, and was due primarily to summer grazing overuse by livestock. Our data show that 

 the rainfall intensities expected to occur on such sites are quite substantial. 



Some of the rainfall intensities that can be expected to occur probably will be 

 greater than the infiltration capacities of some sites, particularly those in poor 

 hydrologic condition. Hence, overland flow is almost a certainty. Fortunately, 

 management practices on mountain watersheds can drastically alter runoff volumes and 

 flood peaks. This has been amply and convincingly demonstrated on the Davis County 

 Experimental Watershed (Bailey et al. 1934 and Bailey et al. 1947). On both study areas 

 in the middle 1930's, severe mud-rock floods were generated by storm events with a re- 

 currence interval of only 15 years. Since that time, both vegetal and mechanical 

 rehabilitation measures have resulted in the satisfactory disposition of storm rains of 

 equal or greater magnitude. 



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