Missouri River Recovery Program Shallow Water Habitat Accounting Summary Report. Kansas City District Omaha District 2014

Transcription

1 Missouri River Recovery Program Shallow Water Habitat Accounting Summary Report Kansas City District Omaha District 2014

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3 Contents 1.0 Introduction Overview SWH Definition BiOp SWH Performance Standard Methods Previous Methodology Current Methodology Limitations of Quantifying SWH Results SWH Construction Actions SWH Measurement Uncertainty Conclusion References... 7

4 1.0 Introduction 1.1 Overview Implementation of the U.S. Army Corps of Engineers (USACE) Shallow Water Habitat (SWH) Program is a primary means of compliance with the U.S. Fish and Wildlife Service (USFWS) Biological Opinion on the Operation of the Missouri River Main Stem Reservoir System, Operation and Maintenance of the Missouri River Bank Stabilization and Navigation Project (BSNP), and Operation of the Kansas River Reservoir System which was released in 2000 and amended in 2003 (USFWS 2000, 2003; hereafter, BiOp). The BiOp determined that the continued operations of the Missouri and Kansas reservoir systems as well as the continued operation and maintenance of the BSNP would jeopardize the continued existence of the federally listed Pallid Sturgeon (Scaphirhynchus albus). Creation of SWH is an element of the Reasonable and Prudent Alternative (RPA) intended to aid in the recovery of pallid sturgeon. The SWH Program is being implemented under the authority of the BSNP Fish and Wildlife Mitigation Project (BSNP Mitigation). The content of this report is intended as supporting documentation for the USFWS regarding the USACE s compliance with SWH acreage goals stated in the BiOp. This report provides: (1) a summary of the total amount and distribution of SWH acres available on the system in 2014 compared against the interim check-in target contained in the BiOp; and (2) a summary of SWH construction actions undertaken to date. The geographic extent of the SWH Program is the main-stem Missouri River and adjacent side channels chutes from Ponca, NE downstream to the Missouri s confluence with the Mississippi River near St. Louis, MO. This area includes the entire channelized reach of the Missouri River below Gavins Point Dam, including the minimally engineered reach between Ponca, NE and Sioux City, IA. The BiOp states that the restoration of acres (ac) of SWH per river mile is needed by 2024 and includes performance standards and check-ins related to 30 ac / mile (USFWS 2000, 2003, 2009). As USACE continues towards achieving BiOp compliance and creating SWH, USACE is also working with the USFWS and the Missouri River Recovery Implementation Committee on the development of the Missouri River Recovery Management Plan (Management Plan). The Management Plan will use data and information from the past 14 years to assess whether species performance metrics included in the BiOp and current management actions are the most effective at avoiding jeopardy. Science efforts are being undertaken to confirm and further define the role of SWH for pallid sturgeon. While the Management Plan is being completed, the USACE will focus on meeting the SWH targets provided in the BiOP. 1.2 SWH Definition The 2000 BiOp and amended 2003 BiOp set forth a quantitative definition of SWH as areas where water depth between mid-july and mid-august is greater than 0 but less than 5 feet (0-1.5m) and where flow velocity is between 0 and 2 ft/sec (0-0.6 m/s) (USFWS 2000, 2003). Additional descriptors 1

5 of SWH attributes were provided in a USFWS letter to USACE dated June 29, 2009 (hereafter referred to as clarified definition ). The letter states that SWH: include[s] side channels, backwaters, depositional sandbars detached from the bank, and low lying depositional areas adjacent to shorelines. Key physical components of SWH s are their dynamic nature with depositional and erosive areas, predominance of shallow depths intermixed with deeper holes and secondary side channels, lower velocities, and high-water temperatures than main channel habitats. SWH is thought to benefit young and small-bodied fishes in multiple ways when provided in synchronization with life-stage needs. It is hypothesized that SWH benefits pallid sturgeon by slowing larval drift and increasing retention of larval fish, by providing nursery areas for larval and young-of-year (YOY) fishes, and by increasing production and retention of food sources in these areas of the Missouri River (USACE and USFWS, 2012). 1.3 BiOp SWH Performance Standard The BiOp presents an RPA that contains requirements for the restoration of SWH in the channelized portion of the Missouri River. The BiOp requires approximately 12,035 to 19,565 ac of additional SWH above a baseline estimate of 3,025 acres that was identified in the BiOp, by 2024 (USFWS 2000, 2003, 2009). To monitor progress toward the overall restoration goal, SWH acreage performance standards were established in the BiOp and require 30% (3,611 5,870 ac) above the baseline estimate (3,025 acres) by However, in a letter from the USFWS to the USACE dated October 23, 2009, the 2010 and subsequent targets were delayed by 4 years as a result of the USACE implementing the Yellowstone Intake Fish Passage Project. The BiOp divided the river into numbered segments based primarily on the geomorphic influence of major tributaries. The segments are numbered 11 through 15 (Figure 1) and increase in a downstream direction changing at major tributaries. Per the BiOp, the restoration of shallow water habitat (30 acres/mile) above the baseline estimate should be distributed as follows for USACE s performance standard target. Ponca, NE to Sioux City, IA (Segment 11) 504 total acres Sioux City, IA to Platte River (Segment 12) 3,948 total acres Platte River to Kansas City, MO (Segment 13 ) 5,791 total acres Kansas City, MO to Osage River (Segment 14) 6,020 total acres Osage River to the mouth of the Missouri River (Segment 15) 3,302 total acres The 2014 check-in requires 30% of the above-mentioned acres on top of the baseline estimate at the 30 acres/mile performance standard. Table 1 identifies the acreage amount of habitat to be restored based on 30 acres/mile and the baseline estimate of 3,025 acres broken down by each segment. The two of these combined, provided the total goal amount of SWH for In Table 1, using Segment 12 as an example, the river segment length is 140 miles. Based on the performance standard of 30 ac/mile, the final total acreage for this segment is 4,200 acres. However, the BiOp baseline acreage estimate for Segment 12 is 252 acres and should be deducted from this total. 2

6 Therefore, the total amount to restore for Segment 12 is adjusted to 3,948 acres. For the 2014 Check-In Report, the amount of habitat to restore is 1,184 acres, which is 30 percent of the adjusted 3,948 acres. These two numbers combined, equal 1,436 acres, and is the amount of habitat required for the 2014 Check-In Report. Table 1. BiOp SWH performance standard target by river segment (30 ac/mi target ). BiOp Segment Geographic Range River Mile Range Segment Length 2003 BiOp SWH Baseline Acres Performance Standard Target for Target based on 30 acres/mile (acres) Total = 2014 Target BiOp SWH baseline acres RM mi Acres Acres 11 Ponca, NE to Sioux City, IA Sioux City, IA to Platte River ,184 1, Platte River to Kansas River ,049 1,737 2, Kansas River to Osage River ,090 1,806 2, Osage River to the Mouth ,589 Totals 3,025 5,870 8,895 Figure 1. Map of the Lower Missouri River extending from Gavins Point Dam showing river segments as outlined in the BiOp. 3

7 2.0 Methods 2.1 Previous Methodology Estimates of 2003 SWH acreage in the BiOp (USFWS, 2003) were based on physical habitat models developed during the biological assessment performed by USACE (USACE, 2003). Estimates were derived from seven representative sites that were each 1 to 2 miles in length within the Lower River below Gavins Point Dam. SWH acreage estimates at each site was based on the results of twodimensional hydraulic model computed depth and velocity outputs that were spatially evaluated with GIS tools. The results of this analysis were recorded as 3,025 ac within the BiOp. 2.2 Current Methodology The methodology in this report uses a far more spatially comprehensive dataset than past efforts. The data sources for this report include a hydrographic survey dataset collected in 2012 (river miles 735 to 500) and in 2013 (river miles 500 to 0), and a 2014 Light Detection and Ranging (LiDAR) dataset collected at low winter stages that captured all exposed bed and banks from Gavins Point Dam to the mouth (RM 811-0). The combination of these two improved datasets provides survey coverage capable of accurately describing the bed elevations of the entire lower Missouri River. While previous SWH estimates used datasets that covered less than 15% of the river length, the estimates in this report are based on datasets that cover approximately 95% of the current river. The hydrographic survey and LIDAR datasets were processed in geographical information system (GIS) software to develop a terrain model of the Missouri River. The terrain model was then overlaid with hydraulic and hydrologic data to map river bed inundation depths for various Missouri River flows. The resulting inundation mapping model was checked against aerial photographs to verify the model covered the full lateral extent of the river bed. The inundation mapping model developed and used for this report provides a more accurate estimate of the amount of various depth classes of aquatic habitat available over a range of flows. 2.3 Limitations of Quantifying SWH Currently, it is not possible to quantify the acres of SWH currently existing in the Missouri River according to all the descriptors of attributes provided by the USFWS. The technical limitations include: The spatial extent of the river and the temporal nature of the duration of medium August flows prohibit collection of velocities and temperature over more than a small percentage of the river. Quantifying the dynamic nature of aquatic areas requires extensive collection and comparison of multiple hydrographic surveys. Computational models to quantify velocities over an area as large as the Missouri River are not possible to construct within a reasonable timeframe. 4

8 Due to these limitations, it is necessary to quantify SWH using the single attribute of depth of water during median August flows. More specifically, SWH within the remainder of this document refers to aquatic habitat that meets either of the following two criteria: For main channel and natural side-channel chutes: At the water surface profile representing postimpoundment (1967-present) 50% exceedance August flow, areas with depth of less than 5 feet (1.5 meters) but greater than 0 feet. For constructed side-channel chutes and backwaters: The entire wetted surface area at median August flow will be counted due to the fact that, at present, constructed chutes are highly dynamic and still evolving to their final plan-form. It is assumed that constructed chutes and backwaters contain habitat that meets the clarified definition of SWH. 3.0 Results The estimate of SWH existing as of 2014 is presented in Table 2. The estimate includes all mainchannel and natural side-channel chute SWH estimated by the inundation mapping model and the total wetted surface area of constructed side-channel chutes. It is estimated, there is up to 11,211 acres of SWH currently available within the BiOp designated reaches. Therefore, based on the USACE s analysis, there is enough SWH on the system to meet the 2014 check-in performance standard. Table 2. Estimates of shallow water habitat acreage compared with 2003 BiOp base acres and ac/mi targets. River Segment Segment Length (mi) 2014 Target baseline acres Current Total (acres) 1 Current Total (acres/mile) Constructed (acres) ,436 1, ,786 2, ,896 3, ,589 3, Total 753 8,895 11, ,758 1 Previous analyses have shown that the SWH acreage may be reduced by up to 20% in some areas when the velocity criterion is applied. (See Section 3.2) 3.1 SWH Construction Actions SWH construction actions involve either modifications of the BSNP structures (structure modifications) or the excavation of side-channel chutes, revetment chutes, or backwaters through the adjacent floodplain. Various types of structure modifications and/or chutes are used in combinations unique to each bend in the river. Project types typically overlap and tend to occur in tandem to achieve the desired result (e.g., a revetment notch to allow flow into a revetment chute). Table 3 below summarizes the number of SWH construction actions taken since The main channel modifications have contributed SWH acres and have also increased the diversity and dynamic nature of the habitat. It is estimated that construction of off-channel projects has resulted in 5

9 approximately 1,612 ac of SHW and top-width widening projects have created approximately 146 acres of SWH. Table 3. Number of SWH construction actions by river segment. River Segment Dike Notching 1 Major Modification Actions 2 Main Channel Modifications Dike Extension Dike Lowering Revetment Chute Channel Widening Off-Channel Projects Side- Channel Chute Backwater Total # of Actions 1, actions include dike notching, type B notching, rootless dikes, revetment notches, and bank notches. 2 actions include chevron construction and other similar actions 3.2 SWH Measurement Uncertainty The SWH estimate developed within this report is the most accurate assessment to date with the best available information at the time this study was conducted. However, there were several factors and decisions made that could potentially affect the accuracy of the SWH estimate. Some expected sources of uncertainty include: Excluding the velocity criteria of areas <2 feet per second when identifying SWH. (Evaluation of Acoustic Doppler Current Profiler results applied to several sampling locations indicated that approximately 10-20% of the acreage meeting the 5 foot depth criteria includes velocity above 2 ft/sec.) Locations where bathymetric data and LiDAR are both needed to estimate SWH Interpolation between bathymetric cross-sections, grid cell size of river bed surface, and cross-section spacing sensitivity analysis Area within the channel without bathymetric or LiDAR data Hydraulic model uncertainty These factors have been assessed and their impacts to the results of this study have been estimated. These impacts are generally considered either acceptably low or conservatively addressed within the main results of the study. 4.0 Conclusion In contrast to all previous methods used to compute the amount of SWH which relied on extensive extrapolation of results from surveyed areas to un-surveyed areas, the SWH estimates 6

10 in this report utilizes survey data sets that cover the entire river. Consequently, the level of accuracy in this report is greater than previous efforts to estimate SWH acreage. Efficiencies in measurement techniques have allowed for an improved estimate of available SWH. The differences between previous estimates of SWH and those reported here do not necessarily represent constructed acres. Rather, the total estimate of up to 11,211 reflects existing acres as of 2014 that have been identified through improved techniques. Acreage estimates should recognize that habitat is dynamic. Any measurement is a snapshot in time. Some recent SWH projects have not yet developed or fully matured to the point they provide creditable habitat. 5.0 References U.S. Fish and Wildlife Service (USFWS) Missouri River Stabilization and navigation Project, Sioux City, Iowa to Mouth detailed Fish and Wildlife Coordination Act Report. Division of Ecological Services, Kansas City Area Office, North Kansas City, Missouri. U.S. Fish and Wildlife Service (USFWS) Biological opinion on the operation of the Missouri River main stem Reservoir system, operation and maintenance of the Missouri River bank stabilization and navigation project, and operation of the Kansas River reservoir system: U.S. Fish and Wildlife Service, 286 p. U.S. Fish and Wildlife Service (USFWS) Amendment to the 2000 Biological Opinion on the Operation of the Missouri River Main Stem Reservoir System, Operation and Maintenance of the Missouri River Bank Stabilization and Navigation Project, and Operation of the Kansas River Reservoir System, U.S. Fish and Wildlife Service. U.S. Army Corps of Engineers and U.S. Fish and Wildlife Service Adaptive Management Strategy for Creation of Shallow Water Habitat. 7