Fargo-Moorhead Metropolitan Area Flood Risk Management Project

Transcription

1 Fargo-Moorhead Metropolitan Area Flood Risk Management Project 52ND ANNUAL IOWA ASCE ENVIRONMENTAL & WATER RESOURCES CONFERENCE 03 April 2014 Aaron W. Buesing Senior Hydraulic Engineer Corps of Engineers, St. Paul District US Army Corps of Engineers

2 Presentation Outline Reason for Project Summary of Feasibility and Environmental Impact Study (FEIS) Changes since the FEIS and subsequent Environmental Assessment (EA) Ongoing studies and design efforts Project status 2

3 Total Drainage Area: 45,000 square miles Red River Basin Drainage Area Above Fargo/Moorhead: 6,800 square miles North Dakota Minnesota South Dakota

4 4

5 5

6 6

7 7

8 FEMA (100-year) Floodplain: 8

9 USACE (100-year) Floodplain: 9

10 Existing Flood Risk (FM Metro) 100 Year Flood 1% Chance 500 Year Flood.2% Chance

11 Feasibility and Environmental Impact Study (FEIS) September 2008: Fargo-Moorhead Metro Feasibility May 2010: Draft Feasibility Report and Environmental Impact Statement released Designs, alignments, and features of several diversion channel alternatives refined Cost estimates for each alternative completed April 2011: Supplemental Draft Feasibility Report and EIS released Several concepts to minimize downstream impacts of a North Dakota diversion plan considered and studied Minimized downstream impacts Caused upstream impacts July 2011: Final Feasibility Report and EIS released All comments received considered Revisions made to incorporate additional analyses and data, and to address comments 11

12 Alternatives Considered Non-Structural Measures Upstream Retention Levees/floodwalls Diversions ND and MN

13 Upstream Retention 400,000 AF of storage needed for 1.6 ft stage reduction during 100 Year flood (USACE) 270,000 AF of storage needed to provide 2 ft reduction during 1997 flood (<50-year) (RRBC) Location of runoff could limit effectiveness Important long-term water management strategy

14 Levees Max. level of protection of approx. a 50-year flood (USACE). Flood insurance may still be required. Est. cost $900 million. Potential upstream and downstream impacts mitigation will increase cost.

15 Diversions Used successfully in Red River basin. Ability to provide 500- year or greater level of flood damage reduction existing and planned levees help to achieve this. Increased area of protection.

16 Hydrology Full Period of Record at USGS Gage 1882, 1897, and 1902 to 2009 Investigated Stationarity Expert Opinion Elicitation (EOE) Panel BUILDING 16 STRONG

17 Peak Discharge (cfs) 35,000 30,000 Fargo Flood USGS Gage Flood stage exceeded 50 times in past 112 years Trend of larger floods Largest 3 floods since ,000 20,000 15,000 10,000 5, Year

18 Maximum Daily Flow Rate (cubic-feet per second) 70,000 Red River of the North at Fargo, North Dakota Lack of stationarity in flood flow frequency and magnitude since the 1940s is indicative of transitions from dry to wet-cycles. 60,000 50, flood have exceeded the "Major Flood Stage" since of the 13 "major" floods have occured since Regional wet-cycle has caused recent extreme floods elsewhere in North Dakota. 500-Year Flood 100-Year Flood Event 40,000 30,000 The 2009 flood is the largest flood on record and equates to a 50-Year Flood Event. 20,000 10,000 Approximate Major Flood Stage ?

19 Maximum Daily Flow Rate (cubic-feet per second) Red River of the North at Fargo, North Dakota 35,000 Full Period of Record 30,000 Wet Period 25,000 FEMA Period of Record 20,000 15,000 Approximate Major Flood Stage 10,000 5, ? Source: USGS river flow data from USGS Station

20 EOE Experts David Ford, PhD Facilitator, David Ford Consultants Michael Deering, PE, D.WRE Senior Hydraulic Engineer, Water Resource System Division, USACE Hydrologic Engineering Center Scott Dummer, Hydrologist-in-Charge, National Weather Service North Central River Forecast Center, Chanhassen, MN Robert Hirsch, PhD Research Hydrologist, US Geological Survey (USGS) National Research Program Rolf Olsen, PhD Water Resources Systems Engineer, USACE Institute for Water Resources David Raff, PhD, PE Technical Specialist, Flood Hydrology and Emergency Management Group, Technical Services Center, US Bureau of Reclamation (USBR) Aldo (Skip) Vecchia, PhD Research Statistician, USGS North Dakota

21 EOE Results experts rather quickly moved away from a discussion of climate change, per se, and focused instead on the apparent lack of stationarity in the flood flow frequency and magnitude data over the period of record (the last 110 years or so).

22 EOE Results Defined the dry period as and the wet period as Use statistical tests for homogeneity to determine where to divide the POR. The expert panel did not agree on the statistical tests, but did note work by Villarini, et al Used PETTITT test

23 Pettitt Test Statistics of Change N 108 K T+ 0 K T K T 1790 Year Change Point 1941 Standardized K p oa (significance Probability associated with K T- ) p oa (significance probability associated with K T ) 2.710E E- 7 Significance Probability Pettitt Test at Fargo, ND Year Change Point: 1941

24 Pettitt Test Significance Probability Pettitt Test: Grand Forks, ND Statistics of Change Number of Years in Series, N 128 K T+ 233 K T K T 1913 Change Point Year P oa P oa, K T E E-05 Pettitt Test for Grand Forks, ND % % % Year

25 Devils Lake

26 FEMA Effective FIS Hydrology Summary Red River of the North Regional Flood Analysis, Breckenridge to International Boundary (1971) Administrative agreement between NDSWC, MN DNR, NRCS, USACE, and USGS Carried forward as part of ongoing map updates. USACE Full Period of Record Analyzed full period of record (1882, 1897, and 1902 to 2009) USACE Wet Cycle Analyzed Wet portion of the period of record (1942 to 2009). Does not include data from 2010 and 2011 flood events. End date for wet cycle is unknown. BUILDING 26 STRONG

27 Peak Discharge (cfs) 35,000 Fargo Flood USGS Gage 30, yr 100-yr COE, Period of 100-yr COE, Expert 50-yr COE, Expert 25, yr COE, Period of 20, yr 15, yr COE, Expert 10-yr COE, Period of 10, yr 5, Year

28 Economic Analysis Flows at a Given Exceedance Probability 10-yr 100-yr 500-yr Year 0: Wet Period 17,000 34,700 61,700 Year 25: Combine: 0.8 Wet, 0.2 Dry 15,394 32,921 57,641 Year 50: Combine: 0.65 Wet, 0.35 dry 13,965 31,304 54,034

29 Hydraulic Design Analysis to size channel and hydraulic structures. Utilized HEC-RAS computer program. Initially used steady state HEC-RAS for hydraulic design and unsteady HEC- RAS for impact analysis. FEIS design used unsteady HEC-RAS for design.

30 Hydraulic Design 650 river miles, including over 4100 cross sections and 1300 storage areas. Emerson, MB Existing Conditions model developed and diversion alternative added to determine impacts. Lake Traverse

31 HEC-RAS Model 650 river miles, including over 4100 cross sections and 1300 storage areas. Existing Conditions model developed and diversion alternative added to determine impacts. 31

32 Downstream Impacts

33 Downstream Impacts (Phase 3)

34 Downstream Impacts -1.5 day shift ft Wild Rice River, MN Elm River

35 Impact Variability

36 FEIS Plan Separate Storage Area Replaced Existing Reach of Sheyenne Diversion Project Operates for Q > 10,000 cfs Fixed weir diversion inlet 36

37 Environmental Assessment (EA) Items North Alignment West Alignment South Alignment Addition of In-Town Levees Increased Flow Through Town Addition of Gates on the Inlet Structure Oxbow/Bakke/Hickson Ring Levee Supplemental EA finalized September

38 More Flow Through Town / In Town Levees

39 In-Town Levees Advantages The use of levees in town to 35 feet (at Fargo gage) will allow project to operate less frequently (10-year event). Eliminates need for fish passage at Red and Wild Rice structures. Reduces environmental impacts (connectivity and geomorphology) Significantly reduces the probability of summer operation Minimizes impacts to farmers 39

40 Diversion Inlet Gates Feasibility Study Included 90 foot wide fixed weir Advantages of adding adjustable gates o Reduces upstream staging elevations o Adds flexibility in operations o Affects timing of flows in diversion o Provides more control of flow (within design constraints) Variable flows to better match downstream conditions Ability to drawdown staging area faster. Gates will be similar to gates on the Red River Control Structure

41 Oxbow/Hickson/Bakke Ring Levee Currently holding weekly coordination teleconferences 2014 construction start.

42 Federally Recommended Plan 20,000 cfs ND diversion channel 34,000 acre staging area 30-mile diversion 12 miles of tie-back embankments Control structures on the Red & Wild Rice rivers Aqueduct & spillway structures on the Sheyenne & Maple rivers Rock ramp drop structure on the Lower Rush & Rush rivers Meandering low-flow channel Non-structural mitigation for impacts in the storage & staging areas Negligible downstream impacts 42

43 Current Design Reaches Design activities commenced: Outlet/Design Reach1 Design Reach 2 Design Reach 3 (sponsor led) Design Reach 4 Rush River structure Design Reach 5 Lower Rush River structure Design Reach 6 (sponsor led) Design Reach 7 (Maple River aqueduct) Environmental mitigation projects Drayton Dam, Wild Rice Dam, Buffalo River OHB Ring Levee In-Town Levees (sponsor led) Bridges and associated channel BUILDING STRONG designed 43 by the sponsors

44 Current Design Reaches Regional and National Resources used to support design efforts USACE Cold Regions Research and Engineering Laboratory (CRREL) Hydrologic Engineering Center Davis MVS: Rush/Lower Rush, VE teams MVK: Reach 4, VE teams MVM: Reach 5, VE teams MVR: Reach 2, Maple River Physical model, VE teams NWO: Agency Technical Reviews 44 44

45 Conceptual Section of the Diversion Ditching required for lateral drainage Meandering low flow channel Excavated Material Berms (EMB) Recreation

46 Southern Alignment Adjustments Wild Rice Structure Relocation Micro-siting of structure Saves farmsteads I-29 intersection remain in place Alternative structure locations being considered Additional small shifts could be made to save farmsteads 46

47 Project General Operating Plan Project begins operating when it is known that a stage of 35.0 will be reached at the Fargo gage. This will be determined via upstream gages and measurements. Initially a stage of about 30.0 will be held until the peak passes to reduce downstream impacts. Once the peak has passed, the stage will be increased to Fargo stage of 35.0 maintained until pool reaches % event would result in a pool at For events larger than 1% event, pool of maintained while Fargo stage is allowed to rise to % event would result in Fargo stage of 40.0 Flood fighting would occur when Fargo stage is between 35.0 and

48 Project General Operating Plan (continued) For events larger than 0.2% event, Fargo stage of 40.0 maintained while flow to diversion is increased and/or pool is allowed to rise. Spillway set at Once minimum freeboard is achieved due to rising pool, control gates are opened and Fargo stage rises above 40.0, flood fighting stops and city is allowed to flood Evacuation order given in advance of exceeding Fargo stage of 40.0 Operating plan will be clearly documented in the O&M manual 48

49 Operations Plan Study Operation will be based on gage data not forecasting Modeling being completed to identify additional gage sites Upstream Downstream (local inflow) At structures Use historic events Anticipate matrix (if/then) Operation Plan won t be final until construction completed 49

50 Maple River Physical Modeling Description: Allows diversion channel to pass beneath the Maple River Spillway allows floods greater than a bank full event to be diverted to diversion channel River remains biologically connected; maintains fish passage Limits flow to the protected side 50

51 Maple River Aqueduct

52 Rendering Closeup 52

53 Reasons for Detailed Modeling Study Plunging, pressurized flow under aqueduct. Evaluate flow split at the spillway Structure is part of the line of protection Cost of structures warrants investment 53

54 Building size: 17,000 square feet Model physical size: Approximately 80 long, 70 wide Construction materials: Channels: concrete Aqueduct: plexiglass

55 Maple River Physical Model

56 Maple River Aqueduct, Plan View Spillway Maple River Aqueduct Diversion Channel

57 Physical Model Schedule August 2013: Construction restarted January 2014: Construction complete March 2014: Phase 1 completion Calibration, performance verification and testing plan complete June 2014: Intermediate results workshop Summer 2014: Model Tour/Presentation October 2014: Hydraulic optimization report complete December/January 2014: Final aqueduct modeling report 57

58 Oxbow-Hickson-Bakke Ring Levee The approved EA identified a ring levee for this area. Approximately 40 structures need to be removed for the levee Risk and uncertainty analysis used to determine freeboard. Have complete wind and wave analysis Was geotechnically evaluated Freeboard will be 4 feet above the 500 year flood pool level Cass County Highways 81 and 18 will be raised WP-43A is at 65% complete 58 WP-43B is at 45% complete

59 Existing Conditions 100-year Floodplain (USACE)

60 With-Project 100-year Floodplain (USACE)

61 100-year Floodplain Change (USACE)

62 Overall Project Construction Schedule Congress advancing Water Resources Development Act (WRDA) that would authorize the Project The Corps and Local Sponsors are moving forward with the design phase Once authorized and funded by Congress +3 months - Sign Project Partnership Agreement (PPA) years - Project Operable * Executing a Construction Memo of Understanding with the Sponsors that would allow them to begin construction prior to authorization and funding at its own risk * 8.5 year construction period based on $240 Million/year funding stream 62

63 Project Information 63