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Using an Integrated Approach to Characterize Alluvial Fan Flood Hazards – a Case Study on a Highly Managed and Developed Alluvial Fan Christy Leonard U.S

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Using an Integrated Approach to Characterize Alluvial Fan Flood Hazards – a Case Study on a Highly Managed and Developed Alluvial Fan Christy Leonard U.S Using an integrated approach to characterize alluvial fan flood hazards – A case study on a highly managed and developed alluvial fan Christy Leonard U.S. Army Corps of Engineers, Sacramento District, Geotechnical Branch, Geology Section [email protected] BUILDING STRONG® FEMA’s 3-Stage Process . Objective: 1) Define the area where alluvial fan flooding could occur. BUILDING STRONG® FEMA’s 3-Stage Process . Objective: 1) Define the area where alluvial fan flooding could occur. 2) Determine the type of alluvial fan flooding in terms of sediment transport processes. BUILDING STRONG® FEMA’s 3-Stage Process . Objective: 1) Define the area where alluvial fan flooding could occur. 2) Determine the type of alluvial fan flooding in terms of sediment transport processes. 3) Characterize the 1-percent-annual- exceedance flood in areas subject to alluvial fan flooding. BUILDING STRONG® FEMA’s 3-Stage Process . Objective: 1) Define the area where alluvial fan flooding could occur. 2) Determine the type of alluvial fan flooding in terms of sediment transport processes. 3) Characterize the 1-percent-annual- exceedance flood in areas subject to alluvial fan flooding. BUILDING STRONG® FEMA’s 3-Stage Process Stage 1. Recognize and characterize alluvial fan landform. Stage 2. Define areas of active erosion and deposition. Stage 3. Define and characterize the 100- year flood. BUILDING STRONG® FEMA’s 3-Stage Process Stage 1. Recognize and characterize alluvial fan landform. Stage 2. Define areas of active erosion and deposition. Stage 3. Define and characterize the 100- year flood. BUILDING STRONG® FEMA’s 3-Stage Process Stage 1. Recognize and characterize alluvial fan landform. Stage 2. Define areas of active erosion and deposition. Stage 3. Define and characterize the 100- year flood. BUILDING STRONG® Integrated Approach Fan Delineation Topographic Geomorphic Data Flow Lines NRCS Soil Map Contour Lines Slope BUILDING STRONG® Integrated Approach Define Active/Inactive Areas Topographic Geomorphic Data Drainage Network Patterns Soil Development Topographic Roughness Morphometric Variables BUILDING STRONG® Flow Lines Schwanghart, W., Kuhn, N. J. (2010) BUILDING STRONG® Study Area . Located in Central Utah (~5,500 ft. elevation) . Semi-arid climate ► Majority of precipitation falls as snow in the Wasatch Range. ► Summer cloud burst storms. Westward facing canyon feeds the alluvial fan. ► Maximum elevation of contributing watershed: 10,800 ft. BUILDING STRONG® FEMA’s 3-Stage Process Stage 1. Recognize and characterize alluvial fan landform. Stage 2. Define areas of active erosion and deposition. Stage 3. Define and characterize the 100- year flood. BUILDING STRONG® Stage 1: Fan Delineation (Toe) BUILDING STRONG® Stage 1: Fan Delineation (Toe) BUILDING STRONG® Stage 1: Fan Delineation (Toe) BUILDING STRONG® Stage 1: Fan Delineation (Toe) BUILDING STRONG® Stage 1: Fan Delineation (Lateral Bounds) BUILDING STRONG® Stage 1: Fan Delineation (Lateral Bounds) BUILDING STRONG® Stage 1: Fan Delineation (Lateral Bounds) BUILDING STRONG® Stage 1: Fan Delineation BUILDING STRONG® Stage 2: Define Active and Inactive Areas Stage 1. Recognize and characterize alluvial fan landform. Stage 2. Define areas of active erosion and deposition. Stage 3. Define and characterize the 100- year flood. BUILDING STRONG® Stage 2: Define Recent Time BUILDING STRONG® Stage 2: Define Recent Time Geomorphic Timescales (1000s of years)? Engineering Timescales (100s of years)? BUILDING STRONG® Stage 2: Define Recent Time BUILDING STRONG® Stage 2: Define Recent Time BUILDING STRONG® Stage 2: Define Recent Time BUILDING STRONG® Stage 2: Define Recent Time BUILDING STRONG® Stage 2: Geomorphic Map Relative Age Soil Development Drainage Network Topographic Patterns Roughness BUILDING STRONG® Stage 2: Geomorphic Map - Soil BUILDING STRONG® Stage 2: Geomorphic Map - Soil BUILDING STRONG® Stage 2: Geomorphic Map - Soil BUILDING STRONG® Stage 2: Geomorphic Map - Soil BUILDING STRONG® Stage 2: Geomorphic Map Drainage Network Younger Older BUILDING STRONG® Stage 2: Geomorphic Map Drainage Network BUILDING STRONG® Stage 2: Geomorphic Map Topographic Roughness BUILDING STRONG® Stage 2: Geomorphic Map Topographic Roughness BUILDING STRONG® Stage 2: Geomorphic Map BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Morphometric Variables: BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Morphometric Variables: 1) Basin Area BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Morphometric Variables: 1) Basin Area 2) Basin Relief BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Morphometric Variables: 1) Basin Area 2) Basin Relief 3) Feeder Channel Length BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Morphometric Variables: 1) Basin Area 2) Basin Relief 3) Feeder Channel Length 4) Basin Length BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Morphometric Variables: 1) Basin Area 2) Basin Relief 3) Feeder Channel Length 4) Basin Length 5) Fan Length BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Morphometric Variables: 1) Basin Area 2) Basin Relief 3) Feeder Channel Length 4) Basin Length 5) Fan Length 6) Fan Area BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Debris Flow Dominated Fans: • Small basins • Short feeder channels • High relief • Short fan length • Steep fan incline BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Fluvial Dominated Fans: • Large basins • Long feeder channels • Low relief • Long fan length • Shallow fan incline BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type • p = the probability of a debris flow at the given point along the feeder channel; • R = ; . • S = the slope of the feeder channel. BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type R = 0.18 S = 2 Degrees 0.11 or 11% BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Dominate Flooding Type: BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type Fuller, 2012 BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type BUILDING STRONG® Stage 2: Alluvial Fan Flooding Type 1963 Image 2014 Image Settling Basins Historic Channel BUILDING STRONG® Stage 2: Active/Inactive Area BUILDING STRONG® Stage 2: Define Active and Inactive Areas Stage 1. Recognize and characterize alluvial fan landform. Stage 2. Define areas of active erosion and deposition. Stage 3. Define and characterize the 100- year flood. BUILDING STRONG® Questions/References Bertrand, M., Liebault, F., Piegay, H., 2013. Debris‐flow susceptibility of upland catchments. Nat. Hazards 67. doi:10.1007/s11069‐013‐0575‐4 Christenson, G.E., Purcell, C. (Rus), 1985. Correlation and age of Quaternary alluvial‐fan sequences, Basin and Range province, southwestern United States, in: Geological Society of America Special Papers. Geological Society of America, pp. 115–122. FEMA, 2003. Guidelines and Specifications for Flood Hazard Mapping Partners Appendix G: Guidance for Alluvial Fan Flooding Analysis and Mapping. Frankel, K.L., Dolan, J.F., 2007. Characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data. J. Geophys. Res. Earth Surf. 112, F02025. doi:10.1029/2006JF000644 Fuller, J., 2012. Evaluation of Avulsion Potential on Active Alluvial Fans in Central and Western Arizona. House, P.K., 2005. Using Geology to Improve Flood Hazard Management on Alluvial Fans ‐ an Example from Laughlin, Nevada1. J. Am. Water Resour. Assoc. 41, 1431–1447. Kellerhals, R., Chruch, M., 1990. Hazard management on fans, with examples from British Columbia, in: Alluvial Fans: A Field Approach. John Wiley & Sons, New York. Melton, M.A., 1965. The Geomorphic and Paleoclimatic Significance of Alluvial Deposits in Southern Arizona. J. Geol. 73, 1–38. NRC, S., 1996. Alluvial Fan Flooding. Parker, G., Paola, C., Whipple, K.X., Mohrig, D., 1998. Alluvial Fans Formed by Channelized Fluvial and Sheet Flow. I: Theory. J. Hydraul. Eng. 124, 985–995. doi:10.1061/(ASCE)0733‐9429(1998)124:10(985) Reitz, M.D., Jerolmack, D.J., Swenson, J.B., 2010. Flooding and flow path selection on alluvial fans and deltas. Geophys. Res. Lett. 37. doi:http://dx.doi.org.libproxy.uwyo.edu/10.1029/2009GL041985 Santangelo, N., Daunis‐i‐Estadella, J., Di Crescenzo, G., Di Donato, V., Faillace, P.I., Martín‐Fernández, J.A., Romano, P., Santo, A., Scorpio, V., 2012. Topographic predictors of susceptibility to alluvial fan flooding, Southern Apennines. Earth Surf. Process. Landf. 37, 803–817. doi:10.1002/esp.3197 Schwanghart, W., Kuhn, N.J., 2010. TopoToolbox: A set of Matlab functions for topographic analysis. Environ. Model. Softw. 25, 770–781. doi:10.1016/j.envsoft.2009.12.002 Slingerland, R., Smith, N.D., 2004. River Avulsions and Their Deposits. Annu. Rev. Earth Planet. Sci. 32, 257–285. doi:10.1146/annurev.earth.32.101802.120201 USDA, 1950. Watershed Engineering to Accompany Flood Control Survey Report, Seivier Lake Watershed, UT: Appendix No. 2. 57 BUILDING STRONG®.
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