North Peoria Area Drainage Master Plan - Flood Control District of ...

NORTH PEORIAAREA DRAINAGE MASTER PLANshould be used in interpreting and applyingthe results of a Level I evaluation. Watercoursescharacterized with wide geologicfloodplains, multiple or braided channels,highly erosive banks, poorly vegetated banks,and potential for channel avulsions should beevaluated at a higher level than Level I.Areas located within the recommended erosionhazard zones developed as part of theNorth Peoria ADMP may be subject toincreased risks to public safety that warrantspecific development restrictions. Given thelevel of detail used to develop the recommendederosion hazard zones the developer/landowner is given the option of completing amore detailed erosion hazard zone evaluation.A typical scope of work for such an analysis islisted below:• Sediment Yield Analysis• Sediment Gradation AnalysisSpecific tasks likely to be conducted with eachof these analyses are outlined below.Technical Analysis Work PlanTask 1 – Hydraulics AnalysisHydraulic Data – HEC-RAS Models. Hydraulicdata will be obtained from modeling preparedfor the effective FEMA Flood Insurance Studiesor new modeling prepared for this study.Specific tasks include the following:• Convert HEC-2 to HEC-RAS Format. Inaddition to simple translation of the fileformat from line-based HEC-2 input towindow-based HEC-RAS input, the inputfiles will be screened for consistent channelbank stationing, extraneous GR points,and ineffective flow areas.([DPSOHRI8QGHU'HVLJQHG6WUXFWXUDO%DQN3URWHFWLRQTypical Scope of Work for Detailed ErosionHazard AnalysisChannel stability, or the potential for lateralmigration, will be evaluated using the followingtypes of analyses:• Interpretation of Geologic Surfaces• Historical Analyses• Field Analyses• Geomorphic Analyses• Hydraulic and Empirical Analyses• Sediment Transport Modeling• Plot Cross Sections. Cross section plotsshowing existing condition 2-, 10-, and100-year water surface elevations will beprepared. If the future conditions flowrates change significantly from existingcondition flow rates, then water surfaceelevations and channel geometry will alsobe plotted for future conditions. Ineffectiveflow areas in cross sections will alsobe documented.• Prepare Plots of Hydraulic Data from HEC-RAS. Plots of top width, hydraulic depth,flow cross section area, maximum flowdepth, mean channel velocity, and otherdata, as needed, will be prepared. At minimum,data from the 100-year event willbe plotted. Additional plots for the 10-year event may be made to estimate conditionsfor the dominant discharge.• Define Channel Subreaches. Plots of HEC-RAS data will be used to define characteristichydraulic reaches based on uniformflow sections, erosion prone sections (narrowwidth, high velocity), choke sections28