Harpeth River, Tennessee: Technical Appendices
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Harpeth River, Tennessee: Technical Appendices Appendix A: Acronyms & Abbreviations Appendix B: Study Area Maps Appendix C: Scoping Letter, Responses, & Letters of Intent Appendix D: Hydrology & Hydraulics Appendix E: Hazardous, Toxic, & Radioactive Waste Appendix F: References Appendix A Acronyms & Abbreviations (This page intentionally left blank for two sided printing) Appendix A Acronyms & Abbreviations Acronyms and Abbreviations BMP Best Management Practice BWSC Barge, Waggoner, Sumner, and Cannon CE Common Era DO Dissolved Oxygen FEMA Federal Emergency Management Agency FIRM Flood Insurance Rate Map FRM Flood Risk Management HRWA Harpeth River Watershed Association HTRW Hazardous, Toxic, and Radioactive Waste IA Individual Assistance Metro Metropolitan Nashville MS4 Municipal Separate Storm Sewer System NED National Economic Development NER National Ecosystem Restoration SR State Route TDEC Tennessee Department of Environment and Conservation TWRA Tennessee Wildlife Resources Agency WMA Wildlife Management Area WRDA Water Resources Development Act Harpeth River, Tennessee 1 Appendix A May 2012 Appendix B Study Area Maps (This page intentionally left blank for two sided printing) Appendix B Study Area Maps Harpeth River, Tennessee 3 Appendix B May 2012 Appendix B Study Area Maps Harpeth River, Tennessee 4 Appendix B May 2012 Appendix B Study Area Maps Harpeth River, Tennessee 5 Appendix B May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent (This page intentionally left blank for two sided printing) Appendix C Scoping Letter, Responses, and Letters of Intent Scoping Letter Harpeth River, Tennessee 1 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Scoping Letter Responses Harpeth River, Tennessee 2 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Harpeth River, Tennessee 3 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Harpeth River, Tennessee 4 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Harpeth River, Tennessee 5 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Harpeth River, Tennessee 6 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Letters Of Intent Harpeth River, Tennessee 7 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Harpeth River, Tennessee 8 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Harpeth River, Tennessee 9 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Harpeth River, Tennessee 10 Appendix C May 2012 Appendix C Scoping Letter, Responses, and Letters of Intent Harpeth River, Tennessee 11 Appendix C May 2012 Appendix D Hydrology & Hydraulics I. Flood Risk Management Analysis II. Nashville Flood Preparedness (This page intentionally left blank for two sided printing) Appendix D Hydrology & Hydraulics I. Flood Risk Management Analysis As part of the post-May 2010 flood recovery work, separate from this reconnaissance effort, the U.S. Army Corps of Engineers, Nashville District (Corps) began a watershed analysis of the Harpeth River Basin in cooperation with Metropolitan (Metro)-Nashville government. The goal of the work was to develop updated hydrologic information related for flooding within the basin for use in new flood warning tools and for local planning. This information was also provided to the Federal Emergency Management Agency (FEMA) for use in updating local Flood Insurance Rate Maps as part of a current effort within the county. The Corps was provided the newest LiDAR data available in the Metro area, and used State LiDAR data for areas outside Davidson County. The LiDAR data from the confluence with the Cumberland River upstream to the Davidson/Williamson County line was of good quality, but the grid became coarser inside Williamson County. The coarse LiDAR data was acceptable for use with HEC-GeoHMS to collect geometric information for the HEC-HMS rainfall runoff model used in the study, but was deemed inappropriate for use with HEC-GeoRAS to collect geometric data for the HEC-RAS model. Because of this, the Corps created an HMS model of the entire basin, but only created a RAS model of the Harpeth River from the mouth upstream to the Davidson/Williamson County line. The Corps was able to calibrate the models to known events, and replicated the May 2010 inundation. These models were used to perform cursory evaluations of flood risk measures proposed in the study reach as described later in this appendix. For the portion of the basin upstream of Davidson County, the Corps did not create an HEC-RAS model to evaluate alternatives, but a model may be available in the future because FEMA is using the Corps model as a starting point to model the remainder of the river to the headwaters using new LiDAR. A great deal of the assessment, in terms of enumerating at-risk structures, was done by map reconnaissance using available aerial photography. It is recognized that with any vintage photography other than something recently completed there is risk of missing structures that are more recent, or including structures that may have been removed. Flood Risk Management from the Mouth of the Harpeth Through Bellevue, Tennessee The historic May 2010 flood saw flooding in the vicinity of Harpeth Meadows Drive, Hickory Drive, Saunders Lane, Harpeth View Trail, Bluff View Drive, Quail Covey Trail, Riverview Drive, Zapata Drive, Canoe Court, Trading Post Court, Settlers Court, Boone Trace, Beautiful Valley Drive, Settlers Way, Valleypark Drive, Claytie Circle, Londonberry Road, Staffordshire Drive, Sunderland Circle, Rolling River Parkway, Scenic Valley Lane, Somerset Farms Circle, US 70/I-40 Intersection, General George Patton Road, Morton Mill Road, Todd Preis Drive, Plantation Court, Beech Bend Drive, SR 100, Yearling Way, Tern Court, Sparrow Court, Rock Wall Road, and others. This is as far upstream as the Nashville Flood Preparedness HEC-RAS model extends. Each of these streets is in the area of predominantly residential or mixed commercial development. Additionally, the Harpeth River created its own high-flow relief in the vicinity of river mile (RM) 42.65 (near the Kingston Springs exit on I-40) during the May 2010 flood. The flow re-entered the river in the vicinity of RM 38.05. Several structures, including homes, were destroyed or damaged as a result of the river cutting off the bend at this location. A local elementary school, Kingston Springs Elementary School, was flooded by backwater from the river near this location. Flooding of homes during the May 2010 flood along Cunningham Court on the left bank of the Harpeth River in Kingston Springs, Tennessee (vicinity Harpeth River Mile (HRM) 36.2). Based on GIS reconnaissance it appears that 19 homes may have been affected by flooding during this event. Harpeth River, Tennessee 1 Appendix D May 2012 Appendix D Hydrology & Hydraulics Additionally, the sewage treatment plant may have been isolated by floodwaters, if not directly impacted. However, none of these structures are affected by any event less than the May 2010 flood, which exceeded the 0.2% annual chance exceedence event in this area. Staff of the Town of Kingston Springs reported that flood waters from the May 2010 event inundated the lagoon at the treatment plant and damaged a number of sanitary sewer pump stations. In this area the depths of flooding during the May 2010 event were up to approximately four feet. Two options are apparently available in this location. The first may be to raise the homes in place due to the relatively low depth of flooding. However, this method may not be appropriate if the homes are slab- on-grade. Further investigation of this method may be necessary. A second option may be to construct 4,000 linear feet of levee that ties to high ground on each side of the neighborhood. This length would also enclose the treatment plant and preserve access to the plant during a recurrence of the May 2010 event or other flood that would prevent access. The height of the levee would be 22 feet plus any necessary freeboard to protect up to the May 2010 event, and would require a pump station for interior drainage. Flooding of homes during the May 2010 flood along East Kingston Springs Road, Maple Court, Acorn Court, Hickory Drive and Harpeth View Trail on the left bank of the Harpeth River in Kingston Springs, Tennessee. This area is affected by riverine flooding and lies partially along a natural cutoff channel that operates during the 4% annual chance exceedence and larger events. The upstream end of the cutoff is near HRM 42.5, and the outlet is near HRM 37.9. Based on GIS reconnaissance it appears that 35 homes may have been affected by flooding during this event and two homes were completely destroyed. Fewer than 10 of the homes appear to be affected by events smaller than the May 2010 flood. In this area the depths of flooding during a recurrence of the May 2010 event range from 2 feet to 11 feet. There is one home that may be in the revised floodway. All homes except 2 are above the 100 year flood. 500-year flood depths range up to 6 feet. In these structures, depths may be too great to raise (again dependent upon construction type) or for floodproofing, and therefore, the only potential mitigation may be buy-out and evacuation. Flooding of homes during the May 2010 flood along Riverview Drive, Elkmont Place, Bluff View Drive, Riverchase Court and Elkmoore Drive on the left bank of the Harpeth River in Cheatham County, Tennessee (vicinity HRM 45.7). Based on GIS reconnaissance it appears that 27 homes may have been affected by flooding during this event. The homes may also be subject to flooding during the 0.2%, 0.5% and 1% annual chance exceedence events based on the newest, but not yet adopted, stream profiles.