Regional flooding frequency analysis Vermillion River/bayou teche 1940-2018

Agenda Welcome and Introductions – Harold Schoeffler Presentation “A Regional Flooding Frequency Analysis” – Dave Dixon Contributing Speakers Mark R. Wingate, P.E. Deputy District Engineer for Programs and Project Management for the U.S. Army Corps of Engineers New Orleans District Nick Sims, Project Manager with the U.S. Army Corps of Engineers Don Segrera, manager of the Teche Vermilion District David Cheramie, manager of the Bayou Vermilion District Guy Cormier, St. Martin Parish President Bill Fontenot, St. Landry Parish President J. Paul Kemp LSU Hydrologist Monique Boulet, Chief Executive Officer, Acadiana Planning Commission

topics Video Overview of Regional Watershed Understanding what happened during the August 2016 flood Analysis of the August 2016 flood Regional recommendations for prevention of future flood events

Data sources and Observations Noaa U.S. Geological Survey Army Corps of Engineers Observations and Field Trips

Vermillion river Historical Flood events 1940 7’ Higher! #* 1942 1.25’ lower $ 1947 .82’ lower $

Historical Remediation/navigation and Water Quality projects 1957 Dredging of Vermilion Construction of drainage control for Bayou Courtablu to Basin Other Projects and Notes 1982 Commissioned Teche-Vermilion Freshwater Project Late 90s NOAA lowered the flood stage for Vermilion (12’ $ 10’)

Vermilion River >12 ft Flood Frequency Measured and Forecast 1970-2040

Vermilion River >10 ft Flood Frequency Measured and Forecast 2000-2040

Annual Rainfall & Vermilion River Annual Flood Events 1999-2017

Annual Rainfall & Vermilion River Annual Flood Events 1999-2017(2016 Normalized)

Other Areas Red River Bayou Cocodrie Bayou Des Cannes Mermantau River 79.34 Miles Other Areas Red River Bayou Cocodrie Bayou Des Cannes Mermantau River Bayou Cocodrie 57.5 Miles Bayou Des Cannes 34.5 Miles 33.75 Miles Mermantau River

Flood event data Since 1970 Red River at Alexandria $ (79 miles north) Bayou Cocodrie at Clearwater $ (58 Miles north) Bayou Des Cannes near Eunice $# (35 miles northwest) Mermantau River as Mermantau$# (34 miles west) Vermilion River at Lafayette # (steady increases since 1970)

u.S. geological survey 1988 USGS conducted and published a hydrologic features and processes of the Vermilion river study

2016 Flood data

2016 Flood data

2016 Flood data vermilion flood stage bench marks 12 days river was > major flood stage 21 days river was > moderate flood stage 28 days river was > old 12’ flood stage 55 days for river to return to pre-flood stage

Vermilion River data (after August 15 crest) Vermilion river average falls per day -0.16’ / day for 12 days. -.25’ / day for the next 44 days Weather data after the crest Until Oct. 8, rain totaled 6.61 inches(slightly less than normal) August 15 until Oct 8, 37 days with N-NE-NW winds and 18 days with S-SE-SW winds(Predominately favorable 66% of time) No Abnormally High Tides

2016 bayou teche data Keystone dam south of st. Martinsville stage bench marks Days stage in feet 2 >16 7 >14 14 >12 19 >11 40 to return to pre-flood stage

2016 Flood- Vermilion River vs. Bayou Teche key comparisons and Totals Stages 12 days river was at > 16ft stage 2 days bayou was at > 16ft stage 55 days for river to return to pre-flood stage 40 days for bayou to return to pre-flood stage Volumes -Water from North of Lafayette into the River or Teche Approximately 274,253 acre/feet of water flowed south at Surrey Approximately 212,2285 acre/feet of water flowed south at Keystone Total of 486,538 acre/feet of water 486,538 acre/feet of water = 760 square miles! Volumes do NOT INCLUDE water entering the river south of Surrey

Summary and conclusions Greater than 12 ft flood frequencies on Vermilion river INCREASED BY A FACTOR OF 5x SINCE 1970! Local parish coulee maintenance is NOT THE ONLY PROBLEM The Vermilion river is DRAINING VERY SLOWLY The Vermilion river WATERSHED HAS CHANGED

Possible causations Shoaling in the river bottom-last dredging was in 1950’s Flood water flows and backflows into Cypress Island Swamp Inadequate flood gate drainage capacity at Bayou Cortableau- West Atchafalaya Spillway levee Inadequate channel capacity of Bayou Teche (Keystone Dam)

Other potential issues Teche-Vermilion Freshwater Project - Unintended Consequences Red River Navigation Project Increase in development in Lafayette metro area Bridges on river designed in the 50’s causing a dam effect Too many drains into the river

remedies & recommendations Add additional flood gates to the Bayou Courtableu –West Atchafalaya Spillway Levee Provide an alternative drain for the Cypress Island Swamp Add flood control gates in the Keystone dam Dredge the river in conjunction with the parishes coulee cleaning and retention pond efforts Visual Overview of Recommendations

Benefits of executing the recommendations Future Flood Prevention Better water quality in the basin, Cypress Island Swamp, and Lake Fausse Pointe Possibly Lower Flood Insurance Rates Improved community credit rating for bond issues - Some rating entities have threatened to downgrade ratings if communities do not address flooding risks

Takeaways fROm this Meeting and What you can do This Problem CAN BE FIXED! express your concern regarding the lack of action to resolve the regional problems Your U.S. rep(Clay Higgins) Your local parish presidents, mayors, police jurors, and council members There should be a sense of urgency to fix the problem before we have another major flood event

Thank You for your time and consideration of this issue Without your help WE ARE AT RISK Questions and Public Comments