Upper Mississippi River Restoration Program

Transcription

1 Appendix P: Monitoring and Adaptive Management McGregor Lake Habitat Rehabilitation and Enhancement Project Feasibility Report and Integrated Environmental Assessment Upper Mississippi River Restoration Program Mississippi River: Mile 634 St. Paul District Project Sponsor: U.S. Fish and Wildlife Service November 2018

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3 UPPER MISSISSIPPI RIVER RESTORATION PROGRAM FEASIBILITY REPORT WITH INTEGRATED ENVIRONMENTAL ASSESSMENT McGREGOR LAKE HABITAT REHABILITATION AND ENHANCEMENT PROJECT APPENDIX P Monitoring and Adaptive Management Plan

4 Monitoring and Adaptive Management Plan McGREGOR LAKE HABITAT REHABILITATION AND ENHANCEMENT PROJECT UPPER MISSISSIPPI RIVER RESTORATION PROGRAM POOL 10, UPPER MISSISSIPPI RIVER, WISCONSIN 1 Introduction The 1985 Supplemental Appropriations Act (Public Law 99-88) and Section 1103 of the Water Resources Development Act (WRDA) of 1986 (Public Law ) authorized implementation of ecosystem restoration projects to ensure the coordinated development and enhancement of the Upper Mississippi River System (UMRS). Section 2039 of WRDA 2007 directs the Secretary of the Army to ensure, when conducting a Feasibility Study for ecosystem restoration, that the recommended project includes a plan for monitoring the success of the ecosystem restoration. The implementation guidance for Section 2039, in the form of a CECW-PB Memo dated 31 August 2009, also requires that an Adaptive Management Plan be developed for all ecosystem restoration projects. At the programmatic level, knowledge gained from monitoring one project can be applied to other projects. Opportunities for this type of adaptive management are common within the Upper Mississippi River Restoration (UMRR) Program. Using an adaptive management approach during project planning enabled better selection of appropriate design and operating scenarios to meet the McGregor Lake HREP objectives. Lessons learned in designing, constructing, and operating similar restoration projects within the UMRS have been incorporated into the planning and design of this HREP to ensure that the proposed plan represents the most effective design and operation to achieve the project goal and objectives. The adaptive management plan for the McGregor Lake HREP describes and justifies whether adaptive management is needed in relation to the proposed project management alternatives identified in the project feasibility study. This appendix outlines how the results of the project specific monitoring plan would be used to adaptively manage the project, including monitoring targets which demonstrate project success in meeting objectives. The intent of the project delivery team (PDT) was to develop monitoring and adaptive management actions appropriate for the project s goal and objectives. Adaptive management provides a process for making decisions in the face of uncertainty. The primary incentive for implementing an adaptive management plan is to increase the likelihood of achieving desired project outcomes given the identified uncertainties, which can include incomplete description and understanding of relevant ecosystem structure and function; imprecise relationships among project management actions and corresponding outcomes;

5 engineering challenges in implementing project alternatives; and ambiguous management and decision-making processes. Additional uncertainties (i.e., scientific and technological) relating to the proposed project that were identified by the PDT included: Erosion rates Sedimentation rates Presence and introduction of invasive species Future climate change (e.g., flood events, growing season lengths, ice cover, migration patterns) Adaptive management may be achieved through either active or passive adaptive management techniques. Active adaptive management in the McGregor Lake HREP would involve iterative management decisions influenced by the results achieved by project features. Actions of active adaptive management for the project may include the physical modification of project features and documentation of the changing conditions. Passive adaptive management uses the best available information to achieve management objectives, involves updating resource understanding through analysis of the monitoring data, and the incorporation of the updated understanding into future best management practices. For this project, passive adaptive management would include an assessment of feature functionality through observation and the documentation of lessons learned. Table 1: Summary of Monitoring Tasks and Costs Task Name Led By Estimated Cost Years Total A1 Seedling Survival USACE , 3, 6, B1 Map OW Sites USACE B2 Water Quality Monitoring WI/IA DNRs B3 Fall Electrofishing WI/IA DNRs B4 Summer Spawning WI/IA DNRs , 5, , 2, 3, 4, , 5, C1 Emergent Veg Mapping USACE 200 2, E1 Land Cover Mapping USACE 800 5, E2 Erosion Assessment USACE 100, ,000 Passive Amphibian Monitoring WI DNR 10,000 1, 5, 10 30,000 Passive Underfilling Assessment USACE 1,000 1, 2, 5 3,000 Total USACE Total 117,800

6 2 Project Goals and Objectives Because the study area is within the Upper Mississippi River National Wildlife and Fish Refuge, the Refuge management goals and objectives, the FWWG Desired Future Habitat Conditions, together with input from State and Federal agency natural resource managers, were used to guide the development of goals and specific project objectives. However, this study is only one part of a larger cooperative natural resource management effort on the river. The long-term effectiveness of any project will also depend on broader, system-wide management activities. 2.1 Floodplain Forest GOAL A: Increase age and species diversity of floodplain forest. Floodplain forest on the UMR is typically dominated by a few species that are a similar ageclass. This type of imbalance is generally unhealthy and leaves forest susceptible to invasive species. Forests have also become wetter over time, reducing the coverage of hardwood species and limiting the diversity of tree species. This project will aim to improve the quality and quantity (aerial coverage) of forest habitat. Restored floodplain forest will provide important habitat for migratory and resident birds, and other wildlife such as aquatic mammals, turtles, and amphibians. Objective A Improve ecological health of floodplain forests. Habitat Target A: Optimize habitat conditions conducive to healthy floodplain forest habitat. Increase tree species diversity, ensure regeneration in aging forest stands, improve forest structure, and increase forest coverage. Increase coverage of lowland hardwood forest, characterized by oak species, hickory, and hackberry. Performance Criteria A. Within 50 years after project construction, achieve habitat for floodplain forest that is defined as: a. Overstory canopy cover 70 80% b. Overstory Species to include swamp white oak (Quercus bicolor), red oak (Q. rubra), bur oak (Q. macrocarpa) and hickory (Carya spp.). c. Basal area ft2 per acre d. Tree stocking 50% 90% e. Understory cover > 10 % f. Regeneration > 10% of area g. Coarse woody debris present h. Small cavities 2 visible holes per acre i. Den trees/large cavities 1 visible hole per 10 acres j. Invasive (herbaceous) < 10% k. Invasive (woody) < 10% Within 100 years after project construction, achieve these additional criteria: l. Emergent trees > 2 per acre m. Standing dead trees 2 large trees per acre Monitoring Design Task A1: 1-year Planted Seedling Survival and Growth Rationale: The first year following planting is a critical period to determine whether tree seedlings will become established. Low seedling survival combined with low growth rates for

7 surviving seedlings may indicate deficiencies in planting procedures or seedling stock, the presence of significant site related stressors, or seedling-site incompatibility. Regeneration surveys monitoring seedling survival and growth are standard in most large-scale tree planting programs, both within the Corps and in many public and private organizations throughout the country. Results from 1-year survival and growth surveys will allow for modifications in planting plans to account for agents responsible for low seedling survival and growth as well as for mitigation measures to account for these stressors. Methodology: All floodplain forest monitoring will use fixed area plot methods, with conditions defined on the basis of an estimate of tree seedlings per acre in a given condition. 1- year survival and growth surveys will be conducted only on those areas that were planted in the previous year. On newly constructed features with high density plantings, the random plantings methodology for regeneration surveys currently being used on MVP project lands by Environmental Section foresters will be implemented to assess 1-year seeding survival and growth, with a target of sampling 5% of the area using 1/100 th acre fixed area plots, resulting in approximately 5 survey plots per acre. Only planted seedlings will be measured in the 1/100 th acre fixed area plots, using the medium sampling intensity. In addition, at each 1/100 th acre plot location, two natural regeneration tally plots 1/1000 th ac in size will be measured. These plots will have centers approximately 6.6 feet due north of the 1/100 th acre plot center and 6.6 feet due south. Variable soil mixtures will be placed in a small subset of locations (approx. 1.5 acres) to test differences in tree seedling survival and growth with different soil mixes. In these areas, we will target a sample of 15% of the area. Rather than placing plots on a grid within these areas, plots will be randomly located with an equal distribution of plots between the soil placement types and a minimum spacing between plots of equivalent to twice the radius of an individual plot. A permanent marker will be placed at the center of each of these plots and individual trees within the plots will be marked. The high intensity survey method will be used on these plots to allow for measurement of tree height and diameter. A database of growth of individual seedlings in these plots will be maintained over time to assess impacts of soil mixes on tree survival and growth. In underplanting areas, planting densities will vary based on site conditions and some areas may not be planted at all. The same methodology as above will be used for higher density underplanting areas, as defined in the McGregor Lake HREP tree planting plan. For low density planting areas, the row plantings methodology with randomly located transects will be used. Transects will be identified at the time of tree planting to ensure that a row of planted trees is surveyed. The location of each tree will be recorded as a GPS point at this time. Each sample tree will be revisited in year 1 to determine survival and growth. A medium intensity sampling technique will also be used for randomly located transects. No natural regeneration surveys will be implemented in year 1 in underplanting areas. Approximately 100 plots per year will be surveyed in the main constructed feature areas, 25 plots in the soil mixture research area, and 200 transects in the underplanting area. Monitoring Targets (Desired Outcomes): All sites: Planted seedling survival >75% of sampled seedlings and >50% of seedlings with condition codes of 1 or 2 (annual growth of 6 or more inches, dominant leader may or may not be present, less than 10% branch dieback). Constructed features only: 2,100 naturally regenerated tree or shrub seedlings per acre > 1 ft tall.

8 Adaptive Management: If 1-year seedling survival is below 75%, supplemental planting may be required to replace lost seedlings. However, if it is determined that mortality was due to factors that cannot be easily controlled (e.g. inundated microsite, deer or beaver herbivory), replanting in some locations may not be implemented. No action will be taken if first year condition codes do not meet targets, unless it can be clearly determined that herbivory is limiting seedling growth. If herbivory is the limiting factor, targeted deer repellant treatments may need to be considered. If natural regeneration targets are not met, supplemental seeding may be implemented on constructed features. If any of the monitoring targets are not met in contract year 1 or contract year 2, planting plans for the following year may be modified based on interpretation of the drivers causing the less than desirable success rates. Task A2: Long-term Seedling Survival and Growth Rationale: 1-year seedling survival is critical, but seedlings cannot be considered to be successfully established on a site generally until they reach 4.5 feet in height and are considered to be generally free from competition for light. Long-term seedling survival and growth will be critical for determining whether the restoration effort was successful or not in establishing selfsustaining levels of forest regeneration and forest cover. Methodology: The methodology for 1-year seedling survival and growth described above will also be used to assess long-term seedling survival and growth, though the timing will differ. For long-term seedling survival and growth, three surveys will be implemented. Surveys will be conducted for the entire area 3 years, 6 years and 10 years following project completion. In addition, approximately 6 standard forest inventory plots will be located on the standard forest inventory sampling grid (1 plot/2.5 acres) and sampled according to Corps standard forest inventory procedures. These plots may continue to be tracked over time, allowing for a subset of plots to be integrated into future standard forest inventory, should USFWS decide to implement a standard forest inventory protocol in these areas in the future. Monitoring Targets (Desired Outcomes): In year 3, the same targets are desirable for all areas as in year 1, that is, planted seedling survival >75% of sampled seedlings and >50% of seedlings with condition codes of 1 or 2 (annual growth of 6 or more inches, dominant leader may or may not be present, less than 10% branch dieback). For constructed areas, a target of 1,000 surviving planted and naturally regenerated seedlings per acre is desirable, with at least half of this number being >4 feet tall. By year 6, planted seedling survival of 60% of sampled seedlings will be acceptable with >60% of seedlings with condition codes of 1 or 2 (annual growth of 6 or more inches, dominant leader may or may not be present, less than 10% branch dieback). For constructed areas, a target of 750 surviving planted and naturally regenerated seedlings per acre is desirable at year 6, with at least 75% of this number being >4 feet tall. By year 10, planted seedling survival of 50% of sampled seedlings will be acceptable with >75% of seedlings with condition codes of 1 or 2 (annual growth of 6 or more inches, dominant leader may or may not be present, less than 10% branch dieback). For constructed areas, a target of 200 surviving planted and naturally regenerated seedlings per acre is desirable at year 10, with all of these seedling being >4 feet tall and at least 50% having reached 10 ft. tall. Adaptive Management: No replanting will be implemented after completion of the initial planting cycle, so all adaptive management related to performance indicator 3B will be related to

9 herbivory and competition control and will be triggered by seedlings showing lower than desired condition codes. Herbivory protection, such as tree shelters or chemical deterrent may be implemented. Additional herbicide application may also be recommended if herbaceous competition is the primary driver of low condition codes. 2.2 Lacustrine Habitat for Backwater Fish GOAL B: Improve and maintain protected lacustrine habitat for backwater species. Habitat conditions in the McGregor Lake area are considered suboptimal during the growing season and is limited in the winter for backwater fish species. Protecting and improving this habitat type is important as sedimentation and other processes has reduced the abundance of backwater overwintering habitat compared to historical conditions. Many species rely on this habitat type to survive over winter. Objective B Improve habitat quantity and quality for lacustrine species, including creation of discrete, overwintering habitat. The conceptual models developed as part of Upper Mississippi River System Ecosystem Restoration Objectives report (2009) provide a variety of recommendations on performance criteria for evaluating and planning lentic fish habitat restoration. The specific criteria were developed based on the experiences of State and Federal fishery biologists as to what would be desirable to provide suitable habitat for backwater fish species. Habitat Target B1: Increase aerial coverage of overwintering habitat areas. Performance Criteria B1. Immediately after project construction, maintain existing overwintering areas, and create 1 or more overwintering sites. High quality overwintering areas should be less than 2 miles apart. Rationale B1: This assessment will evaluate the effectiveness of project features to create overwintering fish habitat. Monitoring Design Task B1 Overwintering Site Mapping. A detailed map of qualified overwintering sites within the study area will be developed showing pre- and post-construction conditions. This will be based on as-built drawings. This will be immediately after construction has been completed. Adaptive Management: There is no anticipated need for adaptive management for this habitat target. Habitat Target B2: Improve habitat conditions conducive to overwintering habitat in backwaters during winter. Performance Criteria B2. Immediately after project construction, create overwintering sites defined as a combination of: a. Water depth greater than 7.4 feet (based on 80% exceedence during the growing season) in at least 50 percent of areas designated as overwintering habitat. b. DO levels as measured at mid-depth: Spring/summer/winter: greater than 5mg/l c. Water temperature (winter): 4 C 0 over 35 percent of the area,

10 2 to 4 C 0 over 30 percent of the area, 0 to 2 C 0 over 35 percent of the area. d. Winter current velocity less than 0.3 cm/sec over 80 percent of the backwater area. Rationale B2: The combination of these conditions are believed to be critical for defining fish overwintering sites. Additional thought will be given during feasibility to whether these criteria should be further modified for improvement of habitat during summer conditions, while still meeting overwintering habitat needs. Monitoring Design Task B2- Water Quality Sampling. Sampling of water quality and hydraulic data will be conducted in designated fish overwintering areas (treatment and known quality sites) during winter months. For hand measurements, this will require drilling holes in the ice at sites evenly spaced throughout the targeted area, approximately one every 200 to 300 feet in designated areas. Midwinter data will be recorded using hand instruments for DO, temperature, and water velocity throughout the water column. Alternatively, continuous data recorders also may be deployed with periodic hand monitoring to verify logger observations. If instrumentation is not sensitive enough to detect current velocities of 0.01 feet per second, surrogate measures will be used (e.g., temperature). This data may be supplemented using data loggers that record temperature throughout the winter season. A dye study or the use of soluble materials (e.g., gypsum)2 may also be considered to detect flux and the presence of eddies (Petticrew and Kalff 1991). Assessments will be done in the years 2, 5, and 10, post-construction. Adaptive Management: If overwintering areas are not meeting water quality criteria, the interagency team will consider design modifications that would achieve the desired conditions. Habitat Target B3 : Centrarchid abundance in constructed overwintering sites will increase and resemble that of known high quality sites. Performance Criteria B3: Within 10 years post-construction, restore/maintain lentic fish habitat to yield excellent fixed site electro-fishing catch per unit effort of age 1 plus fish in overwintering sites. Fair - Good: o 100 to 200 bluegills/hour o 50 to 100 largemouth bass/hour Good - Excel: o 200 to 300 bluegills/hour o 100 to 150 largemouth bass/hour Excellent: o More than 300 bluegills/hour o More than 150 largemouth bass/hour Rationale B3: Electrofishing is a survey method commonly used to sample fish populations by sending high-voltage through the water, temporarily paralyzing fish and allowing them to be captured, identified, and measured. Electrofishing has been an effective sampling method for HREPs in the past and can help to verify a biological response to the physical changes brought on by the project. A number of fish species congregate in locations that will serve as overwintering areas prior to ice-over conditions. This staging behavior occurs annually in the fall when water temperatures drop in the main channel. Sampling after these temperatures have been reached can increase

11 the likelihood of capturing fish usage and can help managers determine if additional measures should be taken to achieve the desired biological response. Monitoring Design Task B3 Fall Electrofishing Surveys. Standard boat electrofishing surveys will be conducted after fish stage to overwintering sites during late fall. Surveys will be conducted in treatment and known quality sites. Metrics will include number of fish catch-per-unit effort and size distribution to test the null hypothesis that there is no difference in bluegill population (abundance and size distribution) between treatment and nearby known quality overwintering sites. Electrofishing surveys will be conducted annually by IDNR or WIDNR for a period of 5 years or more. Annual summary reports and a final report that includes all data will be provided within one year of the conclusion of electrofishing surveys. Adaptive Management: If surveys do not show that the population matches known quality sites, the interagency team will meet to determine causes and potential adaptive management solutions. Habitat Target B4: Maintain habitat conditions conducive to meeting habitat needs of backwater fish assemblages for periods outside of the winter season. Performance Criteria B4. Maintain habitat conditions meeting needs for aquatic vegetation and substrate conditions for spawning a. Access to substrates of sand and/or gravel available for spawning. b. Aquatic vegetation cover in the range of 40 to 60 percent (summer) and 25 to 50 percent (winter) in off channel areas. Rationale B4: The combination of these conditions are believed to be critical for supporting fish spawning and summer habitat. Monitoring Design Task B4 Monitor Summer Spawning Conditions. The project will be evaluated for potential spawning substrate and aquatic vegetation. Substrate assessment will be conducted by IDNR or WIDNR at years 2, 5, and 10 post-construction. Aquatic vegetation cover will be evaluated with aerial photos. Adaptive Management: There is no anticipated need for adaptive management for this habitat target. 2.3 Emergent vegetation and wetlands GOAL C: Increase emergent vegetation growth. Emergent Aquatic Vegetation (EAV) is suboptimal and could be improved. EAV itself provides important plant diversity, and also adds ecological value given its use by fish and wildlife. Objective C Increase emergent aquatic plant aerial coverage in the project area, with desirable density and species diversity. Habitat Target C: Create habitat conditions conducive to Emergent Aquatic Vegetation. Performance Criteria C. Immediately after project construction, achieve habitat for emergent aquatic vegetation and emergent wetlands/mudflats that are defined as:

12 Emergent aquatic vegetation: a. Less than 2 feet water depths for average river flows. b. Straight line wind fetch less than 3,500 feet for water depths of 2 feet. c. Secchi transparency greater than 0.8 meter on average during the June 1 - September 1 growing season in backwaters. d. Current velocities of 0.0 ft/sec is preferred; less than 0.2 ft/sec is acceptable under all but flood flows. Emergent wetlands/mudflats: a. Emergent wetlands located in proximity to land are optimal. b. Maintain and enhance microtopography within expanses of emergent wetlands/mudflats. c. Create small isolated wetlands by modifying islands. Rationale C: This assessment will evaluate the effectiveness of project features to create Emergent Aquatic Vegetation and related wetland habitat. Monitoring Design Task C1 Emergent Vegetation Assessment. The extent of emergent vegetation created with project feature W1 will be evaluated with aerial photography using the USGS LTRM methodology for creating the Land Cover shapefiles. This assessment will be completed at year 2 and year 5 post-construction. Adaptive Management: If emergent vegetation does not meet expectation for W1, the performance criteria will be evaluate to determine which variables are out of the optimal range. Options for adaptive management include modify the wetland with additions of material to reduce depths. 2.4 Island Erosion GOAL E: Protect aquatic and terrestrial habitat by reducing erosion. Bank erosion is occurring at the upper end of the project area, as well as the natural levee that separates McGregor Lake and the east channel. This threatens backwater habitat by potential break thru flows, floodplain forest loss through erosion, and other habitat risks. This project will aim reduce erosion to protect these habitats. Objective E Minimize land loss and protect backwater habitat and cultural resources. Habitat Target E: Minimize erosion at the upstream end of the project area, as well as the isthmus separating McGregor Lake and the East Channel. Performance Criteria E: Terrestrial area within the project area is equal to or great than the terrestrial area in the 2010 land cover (398 acres). Rationale E: This assessment will evaluate the continued impacts of erosion versus the erosion protection provide by project features. Monitoring Design Task E1 Terrestrial Coverage Assessment. The terrestrial area will be evaluated with aerial photography using the USGS LTRM methodology for creating the land/water layer in the

13 Land Cover shapefiles. This assessment will be completed at year 5 and year 10 postconstruction. Task E2 Erosion Assessment. During project planning, the issue of erosion rate and impacts was controversial. The interagency team agrees to continue to study the issue to determine whether assumed erosion rates and causes were correct. See the below supplement for the detailed erosion assessment plan. Adaptive Management: The supplemental erosion assessment plan has further details regarding adaptive management options to address erosion concerns. 3 Additional Areas for Informal Research 3.1 Wetland Amphbians The Wisconsin DNR has offered to monitor the wetland at W1 and R4 to track changes in amphibian populations pre- and post-project. This will assist us in understanding the benefits of created isolated wetlands. 3.2 Forest Underfilling Areas of existing forest in F4 and F8 will be underfilled with material to raise the elevation. We do not anticipate tree mortality. We will measure the depth of material on the tree trunks and monitor the tree response. This will inform us whether the underfilling caused unexpected mortality to the existing trees. 3.3 Floodplain Forest Design All restoration and enhancement projects involve many kinds of risks construction, cost, invasive species, etc. This section discusses floodplain forest construction in terms of the risks of achieving desired habitat conditions. In the McGregor Lake HREP we are creating floodplain forest from scratch. Any time habitat is reconstructed rather than improved, there are risks that the resulting habitat will not fulfill all the desired habitat conditions due to the many uncertainties and uncontrollable variables. The greater the intensity of measures, the wider the range of influencing variables. For example, a minor thinning of a forest has a low risk of creating undesirable habitat changes, but also a low potential of significantly changing the forest cover type. A more dramatic action, such as converting an agricultural field to a prairie or converting an aquatic area to a floodplain forest, has a high potential to make significant improvements in habitat value, but along with that potential comes higher uncertainty and greater risks of achieving a precise habitat type. In the case of creating floodplain forest, there are several significant interacting variables that we manipulate to achieve the desired conditions. First, the hydrology must fall within the preferred range of the desired vegetation. There are many different hydrologic variables, some of which are more important to some species, while other variables are the controlling conditions for other species. Hydrologic variables including the total number of flooded days per year, the seasonality of the flooding, the maximum and minimum length of consecutive inundation, the depth of inundation, the velocity of the water, and flood deposition of sediment all strongly influence vegetation community composition. For example, a tree that can survive twenty total days of inundation in a growing season may not survive ten consecutive days of

14 inundation. A mature tree that can survive ten consecutive days of inundation of its roots and lower trunk may not survive the same flood as a seedling when its crown is overtopped. In this project, we attempted to provide the correct hydrologic conditions by examining existing mature forest stands (reference sites) of the desired species. However, the only variable that was available for consideration was total days of inundation during the growing season. Other hydrologic variables may be equally or more important, however we do not have enough reference sites or the hydrologic variable analysis to determine which variables are most important for which species and what range of values are optimal for the desired forest type. In addition, the reference sites are based on mature stands of trees. The persistence of mature trees on these sites do not guarantee that young trees of the same species will succeed under the stand's modern hydrologic conditions since the mature trees may have established under a different hydrologic regime a hundred or more years ago. Our assumption is that trees are more likely to be killed by excessive flooding than by lack of flooding, therefore building high islands minimizes the risk, therefore we designed our islands to be constructed at the drier end of the observed reference sites (our target was 10 days of inundation in a growing season). The second important variable is the substrate. We have attempted to match the texture and drainage capacity of the reference sites soil, however, we are unsure whether a mixture of channel sand and flocculent silt will approximate the soil characteristics of a natural river-sorted silt. There may also be differences in macro and micro nutrient availability between the constructed soil and the reference sites. We have designed our substrate mixture to approximate the texture class of the reference sites, and we believe that the resulting substrate will provide an adequate growing medium for trees, assuming that the contractor is able to mix the two sediment types relatively well. Since all the material will come from aquatic environments, it will not initially have the soil microbiota that occur in natural forests systems. Mature forests grow on soil that has developed a living community of fungi, bacteria, insects, worms, and other microbiota. Many tree species are highly dependent on symbiotic relationships with ectomycorrhiza and endomycorrhizae, which assist plants in acquiring nutrients. Newly placed substrate from the river will take several years to develop the biotic community that forests require. This can slow tree growth or preclude certain species that rely on a vibrant soil flora. Over time, the substrate will develop a healthy microbiota. We plan to address the risk of tree mortality in the early years by monitoring the tree success and replanting if needed. We can also reduce this risk by planting a diverse herbaceous understory to support soil health and by using mycorrhizze inoculant at the initial planting. The third variable that interacts with the above two is the distance to water table. Due to both lock and dam operation and local hydrologic conditions, some areas of the floodplain can reach our target ten total days of inundation at just four feet above low control pool. Hydrologic conditions at McGregor fluctuate more than average, so the land must be 9.5 feet above low control pool to achieve the same condition. Our islands will be built with a pure sand base to accommodate the need to dewater the flocculent fine material, so the vegetation will be planted in about five feet of desirable substrate with another four feet of pure sand between the soil mixture and the control pool. In a natural system, the substrate would vary less severely through the soil profile, and there are very few locations where forests grow above layers of pure sand many feet deep. The sand layer will create a barrier to roots seeking water during dry conditions and will also reduce moisture wicking up through the soil via capillary action. This can create a much drier conditions on the constructed islands than on the reference sites. Although we are replicating the total days of flood inundation, the moisture availability during drought

15 conditions will be much lower. The constructed islands will likely be much more drained and droughty than the reference sites and susceptible to stress or mortality during drought conditions. The risk of desiccation can be further reduced by creating subtle surface microtopography to catch rainfall and recharge the soil moisture of the constructed islands. The three variables described above interact to produce hospitable or inhospitable conditions for forest development. Since two of these variables the blended soil texture and deep sand layers are unique conditions not found in naturally occurring floodplain forests, it is impossible to examine these in a natural forest to understand how they may affect forest success. Considering the significance of these risks, we have included many features to reduce the risks described above. Since floodplain forest is the primary objective of this project, high elevation islands composed of deep and well-mixed substrate have been designed to best mimic the reference sites and reduce the risks of both flooding and desiccation. Unlike any HREP constructed in the St. Paul District to date, this project will have over five feet of mixed sand and fines to reduce the risk of desiccation. Previously, islands have been pure sand capped with 9 to 18 inches of fines, sometimes incorporated by disking, sometimes not. This project invests much more into achieving the ideal conditions for a diverse and resilient forest. There are some residual risks. Young trees could be killed by large flood events and trees of any age may be killed by prolonged droughts or fail to thrive due to undeveloped soil microbiota. These risks would be present in almost any potential island design. The cost of reducing these risks further is too high considering that they are unlikely to result in long-term failure of the project objectives. We will plant a diverse mix of tree species adapted to both wetter and drier conditions than the target reference sites, and the species will sort themselves out by thriving in the locations that best suit their needs. At worst case, we may have to replant trees and we may not end up with the exact species mix that we prefer, however, we are confident that the project will succeed in growing a diverse mix of trees.

16 Erosion Supplement to the Monitoring and Adaptive Management Plan 1 Background 1.1 Document Purpose The FWS, IA DNR, and WI DNR have raised concerns that bank erosion is occurring at multiple locations in the McGregor Island Complex resulting in existing or potential future loss to island habitat and risk of inlets and side channels widening. They have requested bank protection at the locations shown in Figure 1. USACE staff have estimated the potential costs and benefits of bank protection and inlet protection. The benefits of the proposed action are difficult to assess because they depend heavily on the assumed rate of bank loss or channel widening. Since the team does not have sufficient information to determine the rate of erosion, it is difficult to justify these project features. With additional information, the team will be better able to determine the need for erosion protection, the best design for protection measures, and the benefits of the features. Knowledge gained studying bank erosion here will benefit multiple efforts on islands of the Mississippi River including but not limited to the UMRR program. 1.2 Existing Bank Protection Project In the late 1990s, an offshore rock mound approximately 3,200 feet in length was constructed at the head of the island to protect the relatively low lying and thin forested natural levee as well as the backwater features (e.g. wetland). The offshore rock mound was designed and constructed with a top elevation of approximately 617 (NAVD88). An offshore rock mound was selected as the preferred treatment type to lessen impacts to mussels and existing vegetation and limit need for access dredging. An in-depth post construction assessment of the performance of this feature has not been formalized to date. However, anecdotal information from USACE and WIDNR staff and a visual inspection from USFWS staff on April 4th 2018, indicates that the feature appears to be adequately performing. 1.3 Past Studies An extensive review of past research and geomorphic assessment for the study area has not been fully completed but it is known that a considerable amount of research and reports for Pool 10 and the Upper Mississippi River (UMR) has been completed. Studies spanning from the 1970s through the early part of the 21 st century have focused on assessing the condition of in-stream and floodplain features including main channel banks, secondary channels and backwater habitat. Generally these studies have focused on providing higher order insight on river processes (e.g. sediment transport and deposition on a geological or post-colonial time scale) and charting river responses related to anthropogenic (e.g. land uses and water management and control) and meteorological inputs on a pool or geomorphic reach comparative scale. The

17 studies were not necessarily on a project level scale or with direct site specific improvements in mind. However, some of the studies used either field or planimetric data from the general McGregor Lake area and island complex. The existing studies assist in providing geomorphic context on various area and time scales that help to establish design criteria, prioritization on a reach level, and expectations. For example, studies that examined the presence and depth of artifacts and stratigraphy, composition and radiocarbon dating of overbank deposits near the project site provide context that the upper extent of pool 10 (i.e. upstream of Wisconsin River) is prone to aggrading/sedimentation, the channel islands on a geological scale are relatively undisturbed and have maintained a stable position (Benedetti, 2000), and help guide future geomorphic assessment efforts (e.g. field cues to examine). However, relying on past studies and saying the work is over, is not valid as natural fluvial systems are not static over time nor are research and project objectives one in the same. Therefore, new data needs to be collected, compared to past data sets and evaluated during the decision process. 1.4 Geomorphic Response Due to Identified Shift in Hydrologic Regime Appendix H of the McGregor Lake Habitat Rehabilitation and Enhancement Project Feasibility Report and Integrated Environmental Assessment noted a statistically significant trend of increasing average annual discharge for the period of 1938 to 2015 based on data from the Mississippi River at McGregor, IA USGS gage. The analysis indicated that a shift in the flow regime occurred in the early 1980s, substantiated by an increase in annual flows, increase in frequency of flows greater than the 50-percent annual exceedance probability flood, higher variability of annual flows and decreasing trend in the number of low flow days compared to the period of record prior to Relative to the entire period of record, increases in flow within the 1981 to 2015 period are not statistically significant, however the shift indicates that the period of record from 1981 to 2015 may represent the new typical flow regime which is higher and more variable. This shift to a wetter hydrologic regime is of importance as channel morphology typically responds to hydrologic conditions over a period of time. However, if the hydrologic regime from 1981 to the present is maintained, as the McGregor report has indicated, it is hypothesized that the geomorphic response will reach a state of dynamic equilibrium. What is unknown is, the geomorphic time scale for equilibrium to be achieved or, if equilibrium has been reached. 1.5 Preliminary Assessment USACE engineers have examined hydraulic output (e.g. shear stresses and velocities) from preliminary 1-D hydraulic modelling efforts, under a variety of flow conditions, and have found that river mechanic forces leading to extensive bank erosion are relatively low. This conclusion is reflective of the flat hydraulic grade line resulting from the presence of the Wisconsin River alluvial fan just downstream of the project area. Waves generated by wind or recreational craft are within normal ranges for the Upper Mississippi River. However, the position of the project at the mid to upper end of the pool results in more variability in the stage hydrograph. Wave action generated either by wind or by boat wakes may impact the stability of the channel banks during sustained periods when the river stage is high. 2 Data Needs and Proposed Approach There is a limited amount of conclusive, historical and recent field photos and a lack of recent field based geomorphic assessment, reporting and topographic surveying to date, for the areas

18 shown in Figure 1. This lack of available field data makes it challenging to understand the extent, cause, and active rate of erosion and make definitive conclusions when the team s analysis has been based on using existing LiDAR, bathymetric, limited field photos and aerial imagery data collected solely for design purposes. Examination of aerial photos indicates that there may be erosion in the locations shown in Figure 1, but it is very difficult to accurately measure erosion at this scale through aerial photos due to potential errors in ortho-rectification, tree shadows, time of year, water elevation, and other variables. It appears that erosion may be occurring on the main navigational side of the island and less on the East Channel side. Without a recent baseline assessment and repeated analysis, the ability to project past or future rate of change, target and prioritize certain extents, and make an informed and justifiable decision is difficult. However based on the limited existing data with site design objectives in mind and USACE desires to investigate agency s concerns, the USACE team recommends that the channel banks and inlets be evaluated for change via a baseline geomorphological assessment and repeated topographic surveys and monitoring. This document describes the monitoring activities, schedule, cost, and criteria for implementing bank and inlet protection measures based on the results. 3 Habitat Goals The overarching habitat goal is to protect floodplain forest and aquatic habitat from degradation specifically due to river mechanic forces. Habitat degradation may also be a result of natural processes like natural tree mortality, animal activity (e.g. beavers), high winds, ice loading, unnatural pressure from invasive species, climate change, etc. These processes may or may not be an indication of unstable banks and therefore any improvements or protection mechanisms, if sought, must be targeted, defensible and ensure the associated habitat benefits outweigh the habitat impacts. The potential routes of degradation due to river mechanic forces include: 1) Loss of floodplain forest due to bank retreat. 2) Degradation of isolated wetlands and backwater habitat due to formation of new hydraulic connections or widening of existing connections and the potential for the introduction of elevated sediment, flow, and organisms into the wetland or backwater. One concern in particular is the reduction in the overwintering value. 4 Habitat Criteria USACE has to consider both the habitat to be protected or improved by any measure and the cost of that measure. The average annual cost per average annual habitat unit (AAC/AAHU) is used to evaluate the relative cost effectiveness of measures. Both the costs and the benefits are not well-defined at this time because the field conditions and projected rate and consequences of erosion is currently unknown. Erosion protection measures to protect the island bank and measures to control channel geometry may be warranted if the average annual cost per average annual habitat unit (AAC/AAHU) is within a reasonable range. The accepted range for AAC/AAHU unit is not an exact fixed threshold, but has generally been around $5,000 or less until recently. The highest AAC/AAHU that has been approved for an HREP is about $10,000. Generally, USACE leadership has been uncomfortable with projects that have exceeded this threshold. Therefore, in this plan, we use $10,000 AAC/AAHU as a potential threshold, as shown in Table 2. The actual threshold would have to be determined in collaboration with the agency partners, St. Paul District USACE, and Mississippi Valley Division USACE.

19 Once the monitoring data has been evaluated, habitat impacts will be evaluated to determine the AAC/AAHU. The following habitat impacts may justify erosion protection measures: 1) An existing isolated wetland or backwater habitat is projected to become degraded via a new connection to the main stem of the Mississippi River or the East Channel. It is likely that if an isolated wetland or backwater habitat were to become connected via a newly defined channel the associated loss of habitat would justify the cost of preventing the break through, though the habitat consequence of this change would need to be evaluated. If monitoring shows that an isolated habitat would become connected, we would evaluate the costs and benefits of preventing or repairing the breakthrough. Erosion protection and other measures may be warranted, depending on the results of the cost-benefit analysis. We will need to find a way to quantify the impacts of the increased connectivity, e.g. impacts to herptile diversity. 2) An existing connected wetland or backwater habitat is projected to become more connected via an existing inlet channel that expands in cross sectional area, increasing the flow into the backwater, and increasing sediment deposition. Protection of the channel cross section would be justified depending on the results of the cost-benefit analysis. 3) Floodplain forest loss rate, attributable to river forces, is projected to exceed an acceptable rate of bank retreat, considering the average annual cost to average annual habitat units. According to the theoretical cost ratios in Table 2, erosion rates over 2 feet per year may justify off-shore rock mounds, if $10,000 AAC/AAHU is the threshold. At two feet of bank retreat per year, the AAC/AAHU would be $9,265. Note the average annual cost of $240.50/linear foot is based on preliminary analysis of an offshore rock mound with an above grade height of approximately 5-ft corresponding to a target top elevation of approximately 617 (NGVD88), a top width of 5-ft and side slopes of 1:5:1 (H:V). This design matches closely with the existing rock mound installed at the head of the island. Further insight from the baseline geomorphic assessment described in Section 5.1 will help refine both the costs, benefit, and locations. Floodplain forest was the only habitat type used to calculate benefits in Table 2. 5 Habitat Criteria 5.1 Baseline Geomorphic Assessment To begin and allow for adaptation and upfront guidance of the adaptive management plan, a geomorphic assessment of the existing condition of areas identified in Figure 1 will be completed. Broadly, the geomorphic assessment will: 1. Allow for continued dialog and discussions between agencies 2. Complete a cursory-level literature review of relevant studies that provide overall context of assessment of bank stability, bank deposition or erosion rates, and planform condition of backwater habit on a site scale (e.g. McGregor Lake), and/or pool scale (e.g upper portion of Pool 10). 3. Provide a baseline field based data point that reflects current conditions. 4. Identify and prioritize areas that exhibit a low, medium and high risk of bank retreat, and channel inlet deformation due to river forces. 5. Couple results of item #4 with the identifying and prioritizing areas that exhibit a low, medium and high risk for both loss of floodplain forest and backwater habitat. 6. Provide a cursory estimation on historic and existing rate of bank retreat based on field indicators (e.g. estimate of age and species of existing trees and vegetation nearest

20 shoreline, root density and growth pattern, exposed overbank bank and bed substrate, bed stratification, depth of fine overbank sediment, etc) to generally understand the current stability of existing banks and channel inlets. Note a more accurate estimate on rate of bank and channel inlet dynamics can be made by replicated topographic surveys over a longer period of record. 7. Provide indication of likely cause or drivers for existing loss of floodplain forest. 8. Create a photo record at pre-defined locations through the project area. 9. Comparison and cursory assessment of accuracy of historic imagery and preliminary hydraulic modeling output to existing field conditions. 10. Assessment of stability and performance of existing off-shore rock mound at the head of the Island. 11. Assist in guiding the following; a. Establishing locations for topographic surveys. b. Design criteria c. Refinement or defining of triggers requiring action. 12. Develop preliminary concepts for potential treatment options for general and targeted areas. Concepts will take into account general measured height of exposed banks, woody vegetation elevation, access concerns, and designed criteria established upfront by agencies. Specificity will be added to the items above through active discussion with agencies prior to commencing the baseline assessment. 5.2 Baseline Topographic Survey Based on results of Task 5.1 and the prioritized areas identified in that subtask, topographic surveys of the existing shoreline and existing channel inlets will be collected. For upfront preliminary estimation purposes it is assumed that 15-transects at different locations would be included. These potential locations are shown in Figure 2 but would be discussed and refined further. To supplement these traditional survey techniques (e.g. total station) to collect this data, it may be possible for horizontal Lidar technology or structure in motion collected via a drone to be incorporated and collect additional data along a longer path. However, for planning purposes this technology is not currently included in this scope of work. The survey would be completed in consultation with the staff that completed the geomorphic survey to properly collect and code data at pertinent points (e.g. bank toe, woody vegetation elevation). In addition, the hydraulic cross section (i.e. bed to overbank elevation) of the existing channel inlets will be surveyed. The water surface elevation at the time of the survey will be collected as well as the averaged inflow will be determined. A stage-flow curve will be developed for the existing inlets (i.e. two of the east channel and one on navigational channel). A comparison of the existing bathymetry and Lidar data to that of the field collected topo data will be made to determine both accuracy of pre-existing data sets and aid in design. 5.3 Baseline Findings Report The findings from Tasks 5.1 and 5.2 will be summarized in a technical memorandum and shared for review and comment with agencies. A recommendation will be made if certain areas require immediate improvements and the preferred treatment type. If the report does not recommend immediate action, then the plan will be to proceed to step Section 5.4 and beyond.

21 5.4 Photo Recording On a continual annual basis or as agreed upon with project partners, during statistically determined low flow periods, without ice and snow present (e.g. September), geo-referenced field photos depicting the existing condition of the banks identified in Figure 1 will be collected offshore via a boat. In addition, field photos during the same calendar year will be collected if a significant weather events occurs. This includes but is not limited to a sustained flooding event, a reported tornado, straight line winds, ice storm or event resulting in substantial damage to the floodplain forest. At a minimum, the photos will be taken at the select location identified in Task 5.1 and dated and named accordingly. Past photos at the same location will be compared with results reported annually in a brief memorandum that will be used eventually as an appendix to subsequent design reports. A recommendation will be also included if the field photos and photo comparison warrants a repeated topographic survey. 5.5 Repeated Topographic Survey Adopting the work under Task 5.2, the topographic survey will be repeated at a minimum at year 5 and again at year 10 to compare the new and earlier bank and channel cross sectional survey data points. In addition, a topographic survey may be conducted based on the recommendation of Task 5.4. A graphical comparison will be created as well as a site specific (e.g. monument point) and reach averaged (e.g. northern end of R4 shown in Figure 1) annual estimate of bank retreat and channel inlet geometry or capacity. The results will be evaluated against the criteria identified in Section 4 as well from the Baseline Findings Report (subtask 5.3). 5.6 Field Visit Confirmation If Task 5.5 determines the triggers established under subtask c have been reached, a field visit at select locations where improvements are warranted will completed by USACE investigators and project partners confirm the result, target the proposed treatment length, and aid in proposing possible solutions. The results and recommendations from this task, will be reported and used for soliciting a new project to be conducted. 6 Cost Estimate Table 1 provides a preliminary cost estimate for monitoring and estimating bank erosion. The strategy for accomplishing these tasks, e.g. contractor, in-house, partner agency or academic institution, has yet to be finalized. After this plan is reviewed by partners, we will proceed with reaching out to institutions who may be able to provide resources. The cost estimate is a very rough guess, subject to change if the scope and lead agency changes.

22 Table 2: Rough Cost Estimate for Erosion Monitoring Activities Subtask Description Led By Estimated Cost Notes - Contracting and USACE $3,000 Management 5.1 Baseline Geomorphic Assessment (2018) $20,000 to $40,000 Unknown Consultant/ University Hourly Rate of $125 16hrs Lit Review 16hrs Field Prep 2 days in field, 1 day travel, 2 staff members with $2k on lodging and gear expenses 16hrs for Concepts 4hrs for meetings 8hrs for management 5.2 Baseline Topographic Survey (2018) 5.3 Baseline Findings Report (2018) 5.4 Photo Recording Per Year 5.5 Repeated Topographic Survey (2023) 5.5 Repeated Topographic Survey (2028) 5.6 Field Visit Confirmation USACE $18,000 1 week for survey ($16k), 16hrs for H&H involvement Unknown Consultant/ University $3,000 Hourly Rate of $125 2hrs for USACE review 16hrs for Consultant/University 2hrs for meetings (x3 staff) Project Partners $2000 per year Two staff x 8hrs USACE $21,000 3% inflation per year over 5year USACE $23,500 3% inflation per year over 10year USACE and Project Partners Total Estimate Over 10yr Period $6,000 4 staff for 8hr at $175/hr $94,500 - Sans subtask 5.4 $114,500

23 Figure 1: Areas of Observed Erosion and Requested Protection

24 Rate of Erosio n (ft/yr) Table 3: Cost-Benefit Analysis of Floodplain Forest Loss v Erosion Rate Acres lost/ mile/ year Acres lost/ mile/ 50 years AAH U Gain Const. Cost/mile* Estimate d IDC Avg Ann Cost AAC/ AAHU $1,269,840 $48,990 $48,849 $74, $1,269,840 $48,990 $48,849 $37, $1,269,840 $48,990 $48,849 $24, $1,269,840 $48,990 $48,849 $18, $1,269,840 $48,990 $48,849 $14, $1,269,840 $48,990 $48,849 $12, $1,269,840 $48,990 $48,849 $10, $1,269,840 $48,990 $48,849 $9, $1,269,840 $48,990 $48,849 $8, $1,269,840 $48,990 $48,849 $7,412

25 Figure 2: Potential Transect Monitoring Locations Bibliography: 1. McGregor Appendix H 2. Benedetti, RECENT FLOODS AND SEDIMENT TRANSPORT IN THE UPPER MISSISSIPPI RIVER. University of Wisconsin-Madison