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i <br /> <br /> ' URS Greiner Woodward Clyde <br /> the floodway water surface elevations, the floodway locations, and the floodway top <br /> widths are also required between the two studies. Note that to meet FEMA's <br /> requirement for effective tie-in, the new detailed study will be tieing in to a model <br /> representing 1980s' conditions since the previous FIS was performed in the 1980s. <br /> In addition, the 1135 enhancement project has recently been constructed in the Lower <br /> Amazon Creek by the Army Corps of Engineers with the sponsorship and participation of <br /> the City of Eugene. This project involved levee relocation, riparian restoration, <br /> floodplain restoration, and wetland restoration and enhancement. The levee relocation, <br /> riparian restoration and floodplain restoration work is complete now. It will take several <br /> years to complete establishment of the wetland enhancement. Because this project will <br /> affect the floodplain boundaries adjacent to it, the impact of the 1135 project will be <br /> evaluated and included in this detailed hydraulic study for the Lower Amazon Creek. <br /> The City will also be pursuing additional floodplain restoration credit through the CRS <br /> program. <br /> To support the detailed hydraulic analyses, FEMA requires three models be submitted <br /> along with all necessary application forms. The three models are a duplicate effective <br /> model, an existing conditions model, and apost-project conditions model. The following <br /> is a brief description of each model. <br /> 1. The duplicate effective model -this is the model used in the previous FIS study. A <br /> copy of the duplicate effective model can be obtained from the FEMA library. The <br /> results for the 10-, 50-, 100-, and 500-year discharge rates and the floodway are used <br /> to establish abase-line model or effective tie-in. If an alternative hydraulic model is <br /> used, it must be shown that the use of the original model is inappropriate and the new <br /> model must be calibrated to reproduce the previous FIS profiles within 0.1 foot. <br /> 2. The existing conditions model -this model is required to support conclusions <br /> regarding the actual impacts of the 1135 project and to establish more up-to-date <br /> hydraulic conditions. Effective tie-ins should be included in this model if only a <br /> portion of the stream reach is included in the new study. This existing conditions <br /> model should be used as the benchmark for comparing with the post-project <br /> conditions model. <br /> 3. The post-project conditions model -this model should be developed based on the <br /> existing conditions model and should reflect proposed projects for the stream reach <br /> studied. The model is used to evaluate the impact of the project(s) to the flood <br /> height, flood plain width, floodplain location and floodway area. <br /> All detailed hydraulic analyses should be performed using FEMA-accepted hydraulic <br /> models. A list of the FEMA accepted hydraulic models is in the Appendix to this <br /> proposal. <br /> Once the results from these models are produced, the 100-year floodplain and floodway, <br /> and 500-year floodplain boundaries should be identified and delineated on hard copy <br /> maps of the study area. The maps, hydrologic and hydraulic models, along with all <br /> necessary LOMR application forms should be submitted to FEMA for approval. <br /> \\Por2\PROI-WC1945(M2na\TASK03001AMAZ.OMFEMA\fema.Joc 4:OR PM 02/25/00 Page 2 <br /> <br />