Little Menomonee River Corridor Ecosystem Restoration Mequon Road Parcel

Home , Menomonee (sculpture), Menomonee River, Milwaukee River

Ozaukee County, WI

Design Report June 20, 2019

Prepared by:

Ozaukee County Planning and Parks Department Fish Passage Program 121 West Main St., PO Box 994 Port Washington, WI 53074 (262) 236‐2005

Table of Contents Introduction ...... 1 Little Menomonee River Geomorphology ...... 3 Geologic Setting ...... 3 Existing Geomorphology ...... 5 Project Design ...... 6 Channel planform ...... 6 Hydrology ...... 8 Hydraulics ...... 10 Stream Habitat Restoration ...... 12 Culvert Replacement ...... 13 Wetland Restoration ...... 14 Alternatives ...... 14 References ...... 15

INTRODUCTION The Little Menomonee River, a tributary to the Menomonee River, drains roughly 22 sq mi of Ozaukee and Milwaukee Counties in Wisconsin. It flows south for approximately 11 miles from its headwaters north of Freistadt Road in the City of Mequon to its confluence with the Menomonee River near Butler. The headwaters of the river were historically a large wetland, but a ditch was excavated through the wetland to improve drainage for agricultural purposes. The historic wetland was located on the watershed divide between the Little Menomonee River and Pigeon Creek, which flows east and south to the Milwaukee River. The ditch excavated through the wetland connects these two watersheds. The Little Menomonee River is hydrologically connected to the Milwaukee Estuary Area of Concern and has been identified as impaired by the Wisconsin Department of Natural Resources (WDNR) due to poor biological conditions, high fecal coliform concentrations, high chloride concentrations, elevated temperature, and high total phosphorus concentrations. The mostly uniform, straight, agricultural channel sections in the reach within Ozaukee County do not provide favorable habitat conditions for fish and macroinvertebrates.

As part of the Ozaukee County Coastal Resources Ecological Prioritization Master Plan, the Planning and Parks Department (Department), working with multiple partners, developed an Ecological Prioritization GIS Tool (GIS Tool) to better inform preservation and restoration activities. The GIS Tool integrates several natural resource geographic data layers and models related to water quality and hydrology and several layers associated with biodiversity to generate maps that highlight areas that are priorities for preservation and areas that are priorities for restoration, from water quality and flood risk reduction perspectives as well as a more holistic ecological health perspective. It has been used to develop restoration and preservation prioritization maps for several areas of Ozaukee County, including the portion of the Menomonee River watershed that is located within the County. These maps indicate that one of the highest priorities for restoration to improve the ecological, water quality and hydrologic conditions within the streams and riparian corridor is a 56 acre parcel owned by the Milwaukee Metropolitan Sewerage District (MMSD) Greenseams® program along the Little Menomonee River just north of Mequon Road in the City of Mequon (Figure 1).

The Department’s Fish Passage Program has designed stream and wetland habitat restoration along 1270 ft of the Little Menomonee River on this parcel. Objectives of the project include (1) improve geomorphic function of the Little Menomonee River in the project reach by creating a channel that is appropriately sized for its watershed, is connected to a regularly inundated floodplain, and has a self‐sustaining, natural meander geometry, (2) provide high quality, diverse in‐stream and wetland habitat for fish, birds, reptiles, amphibians, and mammals, specifically those that have been identified as species of local conservation interest, (3) demonstrate successful use of the GIS Tool to prioritize and cost‐effectively improve the ecological function of a riparian corridor, (4) improve water quality in the Little Menomonee River and in downstream waters by removing pollutants and decreasing erosion risk through stormwater management, (5) document impacts on water quality through water quality monitoring on the site and within the watershed, and (6) document improvements to the fish and wildlife communities. 1

Figure 1 – Location Map

The design geometry is based on hydraulic geometry curves that were developed for previous wetland stream restoration projects in Ozaukee County (Inter‐Fluve, 2013) and on analysis of hydraulic conditions. This document presents the existing geomorphic and hydrologic conditions of the study area and describes the proposed geometry and hydraulic conditions of the stream.

LITTLE MENOMONEE RIVER GEOMORPHOLOGY Geologic Setting

Glacial ice covered Ozaukee County between approximately 25,000 and 13,000 years ago. Cycles of glacier advance and retreat resulted in the hummocky topography and the deposition of gravelly sand and silty clay found today throughout the county. Toward the end of the glacial period, the ice margin retreated into, and later advanced out of, the Lake Michigan basin several times, expanding and contracting the Lake accordingly. Fine‐grained lake sediment was carried when the ice margin expanded, incorporated into the till, and dropped as the ice melted, producing the silty and clayey sediment that is present in eastern Ozaukee County. The Little Menomonee River flows between an end moraine to the west and a glacial deposit of poorly sorted material with a wide range of sizes (diamicton) to the east and cuts through silty deposits left by a braided stream system that had been flowing through the valley between the end moraine and the parallel receding glacier (Figure 2. Mickelson and Syverson, 1997).

Figure 2 – Geology (excerpted from Wisconsin Geological and Natural History Survey)

By 1836, when the original land survey was completed, the area from the current day confluence of the Little Menomonee River with Little Menomonee Creek to somewhere between current day Friestadt Road and Highland Road was dominated by wetland, and at the time, surveyors estimated that the wetland was draining to the north into Pigeon Creek (Figure 3). According to available topographic data, this wetland was located on the watershed divide and likely drained in both directions. Soil on the project site and within the extent of the historic surveyed wetland is predominantly Ogden mucky peat (NRCS, https://websoilsurvey.sc.egov.usda.gov; 2018).

Wetland spanning Pigeon Creek and Little Menonmonee River watersheds

Project location

Figure 3 – Original Land Survey

Existing Geomorphology

The Little Menomonee River channel was first dredged through the wetland in the early 1900s, and it remains a straight ditch for most of its route through Ozaukee County. The reach upstream of Mequon Road is much wider than would be typical for a natural stream with a watershed area of 3 sq mi, and the lower portion of the reach was excavated to an elevations considerably lower than the invert elevation of the culvert under Mequon Road, perhaps for the purposes of storing water for irrigation during dry periods (Figure 4). Because it is excessively wide and deep, sediment and organic material that enters the stream deposits in the reach, which has resulted in a streambed that consists of unconsolidated silt and organic muck. There are no meanders in the lower part of the reach. However, at the far upstream end of the site, the river has clearly begun to evolve into a more natural stream form as sand and silt have deposited along channel margins to form bars and vegetation has stabilized those bars, resulting in a narrower channel and the start of a meander pattern with portions of connected floodplain at a much lower elevation than the banks of the originally dredged channel (Figure 5).

Figure 4. Little Menomonee River ~350 ft upstream of Mequon Road where the channel remains over‐ widened, deep, stagnant, and disconnected from its original floodplain.

Figure 5. Little Menomonee River approximately 1300 ft upstream of Mequon Road, where a connected floodplain is developing through lateral bar deposition.

PROJECT DESIGN The existing stream channel through the Mequon Road parcel is straight with very little channel heterogeneity. Opportunities for habitat enhancement include formation of a natural meander pattern, restoration of floodplain and wetland connectivity, and construction of habitat elements including pools and wood structure in the stream and wetland restoration adjacent to the stream. The design objectives for the Little Menomonee River are to increase habitat complexity, improve sediment transport through the reach, increase inundation frequency of the adjacent floodplain, avoid increasing the water surface elevation of periodic flood events to satisfy adjacent agricultural interests, and maintain the water surface elevation of the regulatory 100 yr flood event to satisfy local floodplain ordinances and Federal Emergency Management Agency regulations.

The original wetland hydrology on the site was altered when the site was drained with ditches and tile drains. Design objectives for wetland habitat enhancement include increasing the topographic diversity of the site to create a variety of habitats with different hydrologic regimes that target different floral and faunal communities. Channel planform

During previous project design and analysis for other wetland stream restoration projects within the County, empirical relationships were developed to estimate appropriate channel geometry based on analog streams within the region. Streams with relatively flat slopes, watershed area between 1 sq mi and 13 sq mi, and a well‐developed meander pattern that did not appear to have been intentionally manipulated were analyzed with respect to stream form, including sinuosity, meander wavelength, radius of curvature, and bankfull width. These variables were plotted vs. watershed area, and hydraulic geometry relationships were developed as shown in Figure 6. 6

Additional details are provided in the “Ulao Creek Habitat Enhancement Design Report” (Inter‐ Fluve, 2013).

Figure 6 – Hydraulic geometry relationships

At the Mequon Road crossing, the watershed area is approximately 3.0 sq mi (7.8 sq km). The resulting planform dimensions, based on the hydraulic geometry relationships, include a proposed sinuosity of approximately 1.3, a varying meander pattern with a meander wavelength between approximately 50 ft and 100 ft (mean = 71 ft), and a radius of curvature between 8 ft and 15ft (mean = 12 ft). A bankfull channel width of approximately 7‐10 ft is within the range of typical values. A concept alignment was developed using these parameters. The alignment was adjusted further based on a field assessment of potentially impacted trees, consideration of construction around the existing channel, and spoils locations.

The proposed channel top width and depth in the run habitat, derived through iterative hydraulic analysis as described in following sections, are approximately 9 ft and 1.5 ft, respectively. This depth is slightly larger and the width is slightly smaller than dimensions measured near the upstream end of the project, where the stream has begun to recover with floodplain redevelopment through deposition. Pools will be excavated to a maximum depth of 2.5 ft below the top of bank.

Hydrology

Channels generally develop a size and shape that pass the amount of water and sediment delivered to them from upstream during periods of “normal” runoff and flooding (floods occurring once every 1 to 5 years on average). For this project, the geomorphic design goals are to create a channel that passes frequent high flows with minimal channel adjustment (i.e., erosion rates should be within the range of those produced by natural processes) and to promote frequent floodplain inundation to utilize flood storage in the floodplain and make floodplain areas accessible to wetland spawning fish. Therefore, understanding the Little Menomonee River’s flood regime is an integral step in the design process.

For a recently proposed, but not yet approved revision to the regulatory flood mapping for the area, the Southeastern Wisconsin Regional Planning Commission (SEWRPC) and its consultants used the HSPF runoff model to estimate peak flow rates for the 10‐yr, 25‐yr, 50‐yr, 100‐yr, and 500‐ yr events. However, those flows were not calibrated using the available USGS gage flow data at Donges Bay Road, for which 45 years of flow data exist. The USGS gage data was analyzed using PeakFQ, computational software developed by USGS to apply the Bulletin 17C (England et al., 2018) procedures for flood frequency analysis of daily flow data. A comparison of SEWRPC’s flow estimates and the PeakFQ output at the Donges Bay Road gage location shows that SEWRPC’s estimates were approximately 50% ‐ 100% higher than those indicated by the USGS gage data. Because the SEWRPC estimates are based on model results, and the USGS data is based on measurement of water depth and use of a depth‐flow rating curve generated from flow measurements, the PeakFQ analysis of the USGS data is expected to more closely reflect the historic statistical flow rates. Given changing hydrology associated with climate change, future flood flow rates will likely be higher than historic flow rates.

The project site is upstream of the USGS gage at Donges Bay Road, and a significant tributary, Little Menomonee Creek, enters the Little Menomonee River between the two locations. Therefore, the Donges Bay Road flow estimates do not reflect flows at the project site. In addition to the long term record of data at Donges Bay Road, 15‐minute interval data was collected at the Little Menomonee River at Mequon Road and at Little Menomonee Creek at Granville Road in 2008. Typically, one year of data is not sufficient to estimate large flow events, but 2008 happened to be a very wet year, with flows recorded at Donges Bay Road that were comparable to the 1.5‐yr, 2‐yr, 5‐ yr, 10‐yr, and 25‐yr events. These extreme flow events documented at Donges Bay Road in 2008 were used to estimate flows of similar return intervals at Granville Road and Mequon Road. For large rain events, peak flows at the Mequon Road gage ranged from ~19‐25% of those at Donges Bay Road, while peak flows at Granville Road were ~62‐71% of those at Donges Bay Road. Hydrograph patterns at the Granville Road gage were similar in shape to those at Donges Bay Road, but the hydrographs at Mequon Road were distinctly different (Figure 7). This may be due to the relatively large water volume storage associated with remnant wetlands upstream of Mequon Road, slow drainage associated with the very low gradient of the stream, and/or the connection of the watershed to the Pigeon Creek watershed to the north, which might allow the upper watershed to drain in either direction during very high flows. These complicating factors make it difficult to accurately estimate statistical flood flows at the project location.

400

350

300

250

200 Donges Bay Rd

Flow, cfs 150 Mequon Rd LMC_ Granville 100

0 6/7/2008 6/9/2008 6/11/2008 6/13/2008 6/15/2008 6/17/2008 Date

Figure 7 – Flow during and after storm events in June 2008 at the three gage locations. The hydrographs at Donges Bay Rd and Granville Rd have similar shapes, but the Mequon Rd hydrograph does not exhibit similar peaks.

As a final method of estimating statistical flows, regression equations that are based on several significant variables, such as drainage area, stream slope, water storage, soil permeability, etc., which were developed by Walker and Krug (2003) were used to estimate flows from the 2‐yr up to the 100‐yr event. These estimates tended to under‐predict the flow rates at Donges Bay Road and Granville Road, but over‐predict the flow at Mequon Road.

Estimating peak flows at Mequon Road as a percentage of the peak flow at Donges Bay Road determined from the 2008 data was predicted to be the most accurate method for the flood flows that are within the range of flows documented at both gages in 2008. Given that the flows from the SEWRPC model were established as the regulatory flows for the river, those flows are also important to consider. Flows analyzed are summarized in Table 1. Analyzing hydraulic conditions for these flows is intended to reflect a reasonable range and assure that the project will function as desired at all flows.

Table 1. Statistical Flood Flow Rate Estimates

Approximate Peak flow at Recurrence Mequon Road Interval (yrs) (cfs) 2 40 5 60 10 67 25 80 SEWRPC 10 158 SEWRPC 25 187 SEWRPC 50 207 SEWRPC 100 225 SEWRPC 500 263

Hydraulics

The hydraulic performance of several alternative restoration designs was iteratively tested using one‐dimensional HECRAS computational modeling software, to determine the extent to which different configurations would satisfy the objectives of improving sediment transport, reconnecting the channel to the floodplain, maintaining or reducing the water surface elevation of flood events that are more frequent than the 100 yr event to satisfy adjacent agricultural interests, and maintaining the water surface elevation of the regulatory 100 yr flood event to satisfy local floodplain ordinances and Federal Emergency Management Agency regulations.

The design that best satisfies these objectives, within the ranges of natural wetland channels presented in the hydraulic geometry section of this report, consists of a channel with a 9 ft top width, channel depth of 1.5 ft (not including pool depth), 80‐100 ft wide regularly connected floodplain, and removal of the levee on one side of the river to allow extreme flood waters to spread onto the site (Figure 8). The values for the variable associated with the roughness of the stream and floodplain (Manning’s n) that were used in the model reflect the channel and floodplain roughness expected for the anticipated vegetation in the long term – primarily wetland grasses and forbs with a few flood‐tolerant trees in the floodplain, more dense forest in much of the adjacent land outside of the new floodplain, and no vegetation growing on the streambed, but increased roughness associated with higher channel sinuosity and installation of wood for habitat and bank stabilization. The proposed stream bed elevation will be increased through most of the project reach to create a natural slope, in contrast with the existing excavated pool, but it will remain slightly lower than the elevation of a constant grade line from the upstream channel bed to the invert of the culvert at Mequon Road. The existing collapsing culvert will be removed and replaced with a corrugated metal pipe‐arch as described in the following section.

The effect of raising the stream bed and narrowing the channel is an increase in the shear stress through the reach from less than 0.005 lb/ft2 to 0.05 lb/ft2 for a flow of 20 cfs, and significant improvement as flow rates increase also. Shear stresses as low as 0.02 lb/ft2 are sufficient to keep silts and sands moving through the system. The shear stresses will be even higher in the meander bends, which will provide the scour energy needed to maintain pools in those locations. 10

Figure 8 – Schematic of existing (pink) and proposed (black) cross sections at a location where the existing channel had been over‐excavated. The proposed configuration features a narrower channel, but much wider floodplain. At flow rates that approach the adjacent field elevation, the proposed water surface (blue) is lower than the existing water surface (pink).

Figure 9 shows water surface profiles for several different flow rates. Because the proposed condition has a higher bed elevation and is much narrower and more sinuous than the existing channel, an increase in water level is expected for low flows. Because the proposed condition also includes excavation of a floodplain at an elevation that allows for regular inundation, the net cross sectional area available to convey high flows is larger for the proposed condition than for the existing condition. Additionally, replacing the existing collapsing culvert with a larger culvert that has a greater hydraulic capacity reduces the backwatering effect of the culvert. Therefore, low flow water levels are expected to increase under the proposed condition, and water levels during moderately high flows are expected to decrease. These conditions will provide more groundwater storage and better habitat for fish during drought conditions, but less flooding outside of the new floodplain during wet conditions. These benefits are most pronounced within the project area, but extend upstream ~0.8 mi. Upstream of Freistadt Road, there is no anticipated change in water elevations due to the project. For the steady state HECRAS model, continuous flow rate is modeled, and therefore, the reduction in flow associated with additional floodwater storage on the site is not reflected. Therefore, the model does not show the anticipated minor reduction in water levels downstream for high flow conditions.

During extreme flood events, such as the regulatory 100 yr flood, the capacity of the stream to convey flow is limited by the culvert constrictions along the river, including the culvert at Mequon Road. The current farm crossing on the site is overtopped during the 100 yr event, and the proposed replacement of this crossing is designed to not impact the 100 yr flood elevations (see the “Culvert Replacement” section of this report). The results of the hydraulic modeling indicate that the proposed changes in the stream configuration through this project area will not change the regulatory flood elevation or regulatory floodplain extents, and therefore, no revision of the regulatory flood map is necessary.

Modeled Water Surface Elevations 734 Mequon Road Freistadt Road m 733

732 Existing Farm Crossing 731

730

729

728 Elevation, ft 727

726

725

724 Project Reach 723 9.25 9.45 9.65 9.85 10.05 10.25 10.45 10.65 10.85 Station, miles existing 20 cfs existing 40 cfs existing 60 cfs existing 80 cfs existing 10 yr existing 100 yr proposed 20 cfs proposed 40 cfs

Figure 9 – Water surface elevations along the stream for existing conditions and proposed conditions.

Stream Habitat Restoration

Habitat within the newly excavated channel will be augmented by the construction of wood complexes and single log pieces along the channel margins. Large wood in the channel induces scour and deposition within the channel, creating bed variability and habitat heterogeneity. Branches will be installed with the large wood to increase cover for fish. Wood will also be placed strategically to protect banks and minimize risk of channel avulsion in locations where the proposed channel crosses or joins the existing channel.

Bed forms (e.g., pools, riffles, runs, etc.) associated with the existing channel are currently limited to the upstream end of the project area, where the channel has begun to re‐establish a small meander pattern through deposition along lateral bars and where a few larger boulders and large wood induces scour. Due to the flat gradient along the channel, we do not anticipate true riffles forming in this channel. However, we have designed the planform to include bends that will encourage scour to maintain pools. In constructing the channel, shallow pools will be dug in these locations, but we anticipate natural bend scour to maintain them over time. Pools will also be dug

in conjunction with large wood placement, and scour around the logs will maintain pools in the long term. Culvert Replacement

The existing culvert is a composite of a collapsing 5.5 diameter corrugated metal pipe at the upstream end and an approximately 7.9 ft x 5.7 ft pipe arch at the downstream end (Figure 10). This crossing will be moved closer to Mequon Road with a larger culvert that is just slightly larger than the bankfull width of the proposed stream. The proposed culvert is a pipe arch with a 9.33 ft span and 6.25 ft rise. In order to maintain the existing 100 yr flood elevation, the road over the culvert must be set at approximately elevation 729.80 ft. To provide sufficient cover over the pipe, the invert of the culvert must be set approximately 1.86 ft below the stream bed elevation at that location. Setting the culvert below the stream bed elevation also ensures that the culvert will not become perched (and therefore a fish passage barrier) if the channel evolution results in a lower stream profile over time. Significant down cutting of the stream is not anticipated, particularly as long as the Mequon Road culvert remains at its current elevation, but if the Mequon Road culvert is lowered, channel degradation could occur. Given the very low gradient of the stream channel, velocities through the culvert will be sufficiently low and water depths will be sufficiently high to allow for fish passage. The highest velocities estimated using the model are less than 5 ft/s for all flow rates modeled and are less than 3 ft/s for flow rates less than 80 cfs. These velocities are lower than target fish passage velocities for native fish in the area. Because the proposed channel configuration includes a narrow channel that consolidates flow, and the gradient through the reach is low, water depth is predicted to exceed 1 ft for flows as low as 4 cfs. This is deep enough for even relatively large bodied fish to pass.

Figure 10 – Transition from crushed 5.5 ft diameter culvert to larger pipe arch culvert at farm crossing on the Mequon Road parcel. 13

Wetland Restoration

In the areas adjacent to the proposed stream channel and floodplain, native vegetation will be restored to create forested wetland and grassland habitats, and three wetland complexes will be constructed to provide distinct habitats with restored wetland hydrology. The specific wetland habitats will include an ephemeral wooded pool suitable for amphibians and reptiles and less accessible to predatory fish, an emergent marsh that is immediately adjacent to and regularly hydrologically connected to the stream to provide critical habitat for northern pike and other phytophilic spawners, and a deeper wetland with open water and a broad shallow marsh edge to attract migratory waterfowl and shorebirds. Stormwater from offsite may be routed through the deeper waterfowl wetland, if desired in the future, to detain and treat the water before it drains to the emergent spawning marsh. This regular flow of water through the emergent marsh during and after rain events would also reduce the risk that juvenile fish get stranded in pools within the marsh.

The project will require a net excavation of approximately 24,000 cubic yards of soil. We propose reusing this material on site to create additional topographic diversity in the upper floodplain. DNR staff has indicated that if this soil is respread outside the floodplain on the south western area of the parcel that a wetland delineation would not be required because existing wetlands appear to be more prominent on the northern portion of the site (email communication from Jared Seidl, 6/12/19). Alternatives

Alternatives to the proposed project were considered, but no alternative met the objectives of the project within the budget constraints.

No Action. If a “no action” alternative is pursued, the stream through the project reach would remain an ecologically impoverished ditch with no regular connection to a floodplain, and the adjacent lands would remain as drained wetland with no topographic diversity and no ephemeral or permanent pools. This alternative would not meet the objective of improving the ecological function of the stream and wetlands in the area, including improved habitat for target fish and wildlife.

Alternative Stream and/or Wetland Configuration. Different stream geometry configurations were considered, but the proposed configuration is expected to best achieve the objectives of providing habitat, transporting sediment, achieving floodplain connection, and storing floodwaters within the available budget.

Haul excavated soil off site for disposal. Removing all soil from the site was considered, but given the high cost of hauling material off site, this approach would require reducing the scale of the stream and wetland excavations to complete the project within the available budget. Therefore, this alternative provides fewer benefits for fish and wildlife and provides less floodwater management benefit than the preferred alternative. Further, the

greater topographic diversity achievable by utilizing the soil onsite will allow for more diverse hydrologic regimes and a greater potential for higher ecological diversity on the site.

Preferred Alternative. The preferred alternative, described in this report and detailed in the construction drawings, is expected to best meet the project objectives and provide the greatest benefits for fish and wildlife given the available budget.

REFERENCES England, J. F., Jr., Cohn, T. A., Faber, B. A., Stedinger, J. R., Thomas, W. O., Jr., Veilleux, A. G., Kiang, J. E., and Mason, R. R., Jr. 2018. Guidelines for determining flood flow frequency — Bulletin 17C: U. S. Geological Survey Techniques and Methods, Book 4, Chapter B5, 148p. https://doi.org/10.3133/tm4B5.

Inter‐Fluve, Inc. 2013. Ulao Creek Habitat Enhancement, Design Report. Prepared for Ozaukee County Fish Passage Program. 20 pp.

Mickelson, D. M. and Syverson, K. M. 1997. Quaternary Geology of Ozaukee and Washington Counties, Wisconsin. Wisconsin Geological and Natural History Survey. Bulletin 91. 56 pp.

Walker, J.F. and Krug, W.R. 2003. Flood‐frequency characteristics of Wisconsin streams. Water Resources Investigations Report 03‐4250. US Department of the Interior, US Geological Survey.