Laserfiche WebLink
<br />DRAFT <br /> <br />TABLE 2. 14d - 100-YEAR FLOOD LEVELS, ILLINOIS GULCH <br /> <br />---------------------------------------------------------------- <br /> <br />X-SECT. STATION WATER SURF. X-SECT. STATION WATER SURF. <br /> ELEVATION ELEVATION <br /> (MSL) (MSL) <br />---------------------------------------------------------------- <br />1.0 0+00 9611. 83 7.2 15+15 9664.62 <br />1.1 0+30 9613.24 7.3 16+25 9664.62 <br />1.2 0+72 9614.75 7.4 16+35 9665.63 <br />2.0 1+25 9617.16 7.5 17+20 9667.40 <br />2.1 1+65 9617.75 8.0 17+30 9667.82 <br />3.0 2+25 9620.22 8.1 19+95 9674.41 <br />3.1 4+60 9625.06 9.0 22+50 9682.51 <br />3.3 5+95 9633.66 10.0 26+87 9695.14 <br />4.0 7+30 9642.09 10.5 29+47 9701. 97 <br />5.0 8+45 9646.30 11.0 32+37 9712.74 <br />5.1 10+15 9648.02 11.5 33+87 9718.67 <br />6.0 12+15 9654.40 12.0 37+87 9733.62 <br />7.0 13+85 9664.47 13.0 39+50 9744.19 <br />7.1 15+05 9664.62 14.0 42+05 9748.86 <br />Discussion of Results <br /> <br />In determing the 100-year flood levels on the Blue River, French <br />Creek, Sawmill Gulch and Illinois Gulch, a number of significant <br />differences were found between the current analysis and the results <br />presented by FEMA. Many of the differences are due to alterations <br />to the streams as the result of development or attempts at <br />improving the channels themselves. In addition, several of the <br />road crossings have been altered. This can have significant <br />effects, either beneficial or detrimental, depending on the <br />consideration given to flood plain issues in designing the <br />improvements. Some of the descrepencies uncovered have been due <br />to differences in surveying or topographic mapping from which the <br />two studies were compiled. Finally, this analysis includes areas <br />outside those documented by FEMA. The FEMA study results only <br />extend to the Town's corporate limits as they were defined in <br />1979. This study attempted to extend the flood plain analysis to <br />the Master Plan Boundary. Unfortunately, availability of mapping <br />did not permit achievement of this goal. <br /> <br />Through most stream sections the 100-year flood plain is contained <br />in a well defined channel. However, there are areas where it <br />overflows or breaks out of the main channel. Most of the time this <br />is due to flow obstruction, particularly undersized culverts. <br /> <br />The following paragraphs identify and discuss areas where this <br />study's results vary from FEMA's and where flood problems exist. <br /> <br />34 <br />