Laserfiche WebLink
<br />3.2.1 Wonderland Creek <br /> <br />The 1995 regulatory model in Appendix 3 represents the most recent version of the <br />regulatory model of Wonderland Creek. This regulatory analysis used HEC-2 as the <br />hydraulic model. The current LOMR supercedes all earlier submittals. The LOMR uses <br />HEC-RAS version 3.1.1 (USACE, 2003) to identify flood profiles and to delineate <br />floodplains. <br /> <br />Similar to the regulatory model, the Wonderland Creek LOMR terminates upstream at <br />Wonderland Lake. The LOMR joins Goose Creek downstream at Goose Creek <br />regulatory Cross Section 65. Since Goose Creek and its water surface elevations for all <br />flood events are lower than Wonderland Creek at the confluence, starting water surface <br />elevations of Wonderland Creek begin at critical depth. <br /> <br />As noted in the Hydrologic Analysis section, flood peak estimates have been increased <br />significantly downstream of Broadway as a result of the spill from Foumlile Canyon <br />Creek to Wonderland Creek. As a result, water surface elevations in the LOMR cannot <br />be compared directly to regulatory water surface elevations. HEC-RAS models <br />developed for Wonderland Creek are found in Appendix 3. In addition, an HEC-RAS <br />model of the spill area was developed and is presented in Appendix 3. Floodplain <br />profiles and the work maps used to plot the plan view of the 100- and 500-year <br />floodplains are in the roll of 24" x 36" plans. <br /> <br />3.2.2.1 Spills From Fourmile Canyon Creek <br /> <br />Flood peak discharges along Wonderland Creek were defined using the combined <br />Fourmile Canyon Creek and Wonderland Creek hydrologic model discussed in the <br />Hydrologic Analysis section. Flood peaks were hard-coded from the hydrologic model <br />into HEC-RAS. <br /> <br />3.2.2.2 Flow Division Near 28st Street <br /> <br />The culvert below 28th Street does not have adequate capacity to carry the 50-, 100-, or <br />500-year flood peak. Flows overtop the culvert during these events and proceed along <br />28th Street and to the west of 28th Street. Since the culvert is long (approximately 700 <br />feet), it was necessary to devise a method to identify flow distributions and paths on the <br />ground adjacent to the culvert. To do this, a junction was placed just upstream of 28th <br />Street culvert entrance to route surface flows downstream. <br /> <br />A schematic of the flow division modeled in HEC-RAS is shown on Figure 3. The <br />divisions were modeled at junctions using energy-based methods, following <br />recommendations in the HEC-RAS manual. Plows upstream of 28th Street are divided at <br />Junction 1 into two branches; one represents the culvert and the other, representing <br /> <br />-20- <br />