Laserfiche WebLink
We used surveyed measures of the channel geometry To compute The Form <br />• Ratio given by <br />F =Width. <br />Depth <br />Schumm (1960, U.S.G.S., Professional Paper 352-B) has developed a relationship <br />between Form Ratio and M-factor That is indicative of channel stability. The <br />relationship is expressed by the equation, F = 255M-I•08. Exhibit 2.5-23 shows a plot <br />of the data and the above equation that is taken to indicate stability. Deviation <br />above the stability line represents aggradation and below the line a tendency toward <br />degradation. W e have added dashed lines to The plot to delimit data points that <br />deviate from the stability relationship by a factor of three or more and are clearly <br />unstable from Those that are stable and marginally stable. <br />Two locations near TR-bb' and OK-BB' are deemed unstable and indicative of <br />degrading reaches. TR-bb' is located immediately upstream from an identified and <br />surveyed knickpoint in the longitudinal profile of Trout Creek. In this context, <br />degradation is to be expected. The location near OK-BB' is at Haybro, where Oak <br />• Creek is constricted between highway and railroad fills. In This situation, <br />degradation is also expected. <br />The hydrolgic significance of the Terrace deposits on Trout Creek appears to <br />be minor. The study area is underlain predominately by shale members of the <br />Williams Fork Formation. A few interbedded sandstones occur in this section. These <br />rocks occur on The eastern limb of The Twentymile Park Syncline where dips and flow <br />in the permeable sandstone units are westward, away from Trout Creek. Owing to <br />the predominance of shale, bedrock and soils in the study area have relatively low <br />permeabilities. No evidence of ground water has been found in the higher (Qt3 and <br />Qt4~ terraces. The Qt2 terraces, on the west side of Trout Creek contain a perched <br />aquifer in the alluvium. Water is recharged by snowmelt, summer thunderstorms, <br />irrigation and infiltration from unlined irrigation ditches. Discharge of This aquifer <br />is through a line of springs on the east face of the terraces. Flow of the springs <br />appears To be at a maximum during the spring and early summer and is greatly <br />reduced in late summer and fall when many of the seeps dry up. No evidence of a <br />significant hydrologic connection between the Ott aquifer and Trout Creek has been <br />found. Clearly, some of the water in the terraces penetrates a short distance into <br />• the bedrock and the springs contribute small amounts of water To Trout Creek either <br />by surface flow or recharge To the QTI aquifer. <br />Revised 7-81 2.5-65 <br />