Logan River Floodplain Mapping Kedric Curtis, Josh Hogge, Jordan Jarrett, Jared Justensen 4/25/2015 CEE 6190 Photo credit:

Overview Problem Solution Approach Preprocessing Processing Post processing Results Errors Conclusion

Problem * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION * According to the Utah Natural Hazards Handbook (2008). Flood risk is undetermined in many areas of Utah The absence of this information leads to local officials perceiving there is no flood risk In these areas many times the City or County does not participate in the National Flood Insurance Program (NFIP) As a result much of the state's flood loss is not reported Between January 1978 and October 2008 a little over $5.3 million dollars was paid to nearly 800 claims in Utah.

Problem * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION * In 2011, flooding of the Logan River caused significant damage. Map the flood plains of the Logan River between First Dam and Center Street to provide information to Logan City and its Residents.

Solution Approach * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION * ●Pre and Post Processing are done in ArcGIS ●Processing is done in HEC- RAS ●HEC-GeoRAS helps in transferring data between ArcGIS and HEC-RAS

Preprocessing * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION * Digitize River cross sections and alignment Associate Manning’s roughness values based on land cover type

Processing * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION * ●Export geometry into HEC- RAS ●Correct Right and Left Banks ●Run steady state flow analysis ○1000 cfs, 2000 cfs, 2500 cfs, and 3500 cfs ●Output: water surface profiles and extents of each floodplain.

Post Processing Import results from HEC-RAS back into ArcMap using HEC-GeoRAS Correct for ineffective flow areas by using the cute tool and cutting out the correct floodplain. * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION *

Results * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION * ●Some roads will be covered at all flood flow rates ●Flooding will occur at the UWRL parking lot, UWRL new hydraulics modeling lab, Riverside Preschool, and various homes

Results * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION * ●Land parcels and preschool affected ●Deep water levels and high velocities in the river would create dangerous conditions

Errors LIDAR data - trees, vegetation, water surface changes, before/after river restoration Creation of river geometry - cross sections, bank lines, overbank locations Manning’s roughness values - polygon shapes, differences between present day land cover and land cover data from raster used in analysis Ineffective flow areas * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION *

Conclusion The purpose of this study was to map the floodplains of the Logan River using ArcGIS. There are many land parcels, roads, and public access locations that would potentially be inundated with water in the event of a flood. Using the mapped flood plains, Logan City officials will be able to know which areas should be given highest priorities for protection and caution during wet years. * PROBLEM * SOLUTION APPROACH * PREPROCESSING * PROCESSING * POST PROCESSING * RESULTS * ERRORS * CONCLUSION *

Questions Photo credit: