SUMMER SEASON MEANS ITS MOWING TIME
Now that summer has (unofficially) started, it’s time to shift from spring cleaning at your dam to summer maintenance. If your dam has earthen embankments, thorough mowing is an extremely important component of the summer maintenance routine at your dam.
Below, find an example of an unmaintained embankment on the left and a well-maintained embankment on the right.
Why Mowing is Important
Grass cover on earthen embankments is a very effective and inexpensive means to prevent the erosion of embankment surfaces. The stems and root systems of grasses tend to trap fine particles of soil, thus inhibiting the migration of these particles. A good grass cover provides an excellent means against erosion due to runoff caused by rains and can protect the embankment during limited overtopping. Having a grass cover also allows you to easily observe any issues with your embankment such as rodent burrows, seepage, scour, erosion, slumps or slides.
Unfortunately, a very common issue observed during inspections is that embankments are overgrown with trees and woody vegetation. Another common issue is that only portions of the embankments have been mowed.
Trees and woody vegetation can have negative impacts to your dam. The uprooting of trees by strong winds can displace embankment material and weaken the integrity of your dam. The root systems of trees can allow seepage pathways to develop and leave voids in your dam as they die and rot. Water can enter and flow through these pathways and could ultimately cause dam failure.
What to Mow
Ideally, grass cover on earthen embankments would be no more than six inches high. Mowing should include ALL portions of the embankment, not just the top of dam (crest). All portions of the embankment include the upstream slope, top of dam (crest), downstream slope, groins, and 15 feet beyond the toe of the embankment. The accompanying illustration identifies these locations on an earthen embankment.
Who to Contact
Some dams may already have excessive trees and woody vegetation growing on their embankments, which would make it impossible to mow. Also, some dams have very steep slopes which make mowing difficult. Tree removal needs to include removing stumps and roots down to one inch and restoring with appropriate backfill material and seeding. Removing many trees at once, with a full pool of water behind the dam, could lead to failure of the earthen portions of the dam! Before attempting to address these issues yourself, first contact your Regional Water Management Engineer to discuss possible solutions.
Find more information about Vegetation on Dams on the DNR Dam Safety webpages.
ABOVE AVERAGE PRECIPITATION FORECASTED FOR PARTS OF WISCONSIN
Precipitation Forecasts
The NOAA National Weather Service Climate Prediction Center has forecasted that the southern half of Wisconsin will have a 33-40% chance of wetter than normal conditions over the next 3-months (July – September 2020). The rest of the state is expected to experience normal conditions through September. The prediction for the southern half of the state continues the trend in recent years of wetter than normal conditions. Several river gauges throughout Wisconsin, especially in the southwest region of the state, are forecasted to have a 25% chance or greater of long-range flood risk (June – August 2020). Water level data specific to a gage in your area, can be viewed on the National Weather Service site.
Rainfall Intensity
In addition to NWS forecasts of somewhat wetter conditions, the NOAA Climate Prediction Center is warning of a continuing long-term trend of increased intensity and frequency of heavy precipitation events. They are also warning that these events may overwhelm aging infrastructure throughout the nation that was never designed to accommodate these types of precipitation events. These events will affect both rural and urban areas, and in addition, may also adversely affect local water quality due to increased runoff.
Great Lakes water levels have been on an upward trend. During the period of 2017-2020 the Army Corps of Engineers (ACOE) indicates that the great lakes have experienced record rises and record highs, compared to water levels and rises over the last 102 years. The ACOE also stated that the water level of Lake Michigan-Huron has been above average every month since November 2014, a streak of 62 consecutive months. These high-water level trends are predicted to continue through the 2020 season.
For more information:
Local Forecast - weather.gov
Long-Range Outlooks - cpc.ncep.noaa.gov
River Forecasts - water.weather.gov/aphs/forecasts.php
Weather & Climate Data - ncei.noaa.gov
BEAVER - IMPACTS AND MANAGEMENT APPROACHES
It is rather common for DNR Dam Safety staff to receive phone calls from dam owners who are concerned about beaver activity at their dams. Owners want to know the impacts beavers might have on their dams and what can be done to manage the issue. DNR also receives phone calls from landowners where beaver have created dams on their property, where a man-made dam didn’t previously exist.
History and Management: Although beaver seem abundant today, due to fur trapping and logging efforts, some estimates suggest that by the late 1800’s there were only 500 beaver left in Wisconsin. However, trapping of nuisance beaver in Northern Wisconsin followed by relocation efforts caused the beaver population to rebound and eventually led to a thriving population. Demand for beaver fur decreased in the 1980’s leading to reduced trapping efforts. In the late 1980’s legislation was enacted to allow trapping or hunting of beavers year-round without a license or permit if damages were incurred on a landowner’s property. Federal, tribal, state and local governments have developed management plans to effectively manage numbers and the benefits and impacts.
Fun Facts:
Ecosystem and Economic Impacts: The single most common feature of beaver habitat is the presence of water. For security and access to food, beavers engineer the environment around them by building dams to increase flooded depths and expand wetland areas typically on small- and medium-sized low gradient streams, wetlands and lakes. Beaver activities often benefit wildlife and improve ecosystem habitat (for example, reducing peak discharge, decreasing sedimentation downstream, increasing summer stream baseflow and increasing habitat diversity). However, beaver activity can also damage and reduce flows through hydraulic structures such as road crossings or dams. They can also alter a stakeholder’s ability to utilize their land.
Culverts and Dams: Culverts and dams are locations that beavers focus efforts on slowing the flow of water as the sound of water coincides with the feeling of security slipping away. Figures 1-3 display classic beaver activity at hydraulic structures. Beavers have also been known to burrow into road and dam embankments depending on site conditions, particularly into the upstream face below the waterline.
Mitigation Strategies: The “Helpful Sources and References” section below contains identification and mitigation and control strategies for beaver. This information was gathered from FEMA, WDNR, USDA and other sources. These resources, particularly the WDNR Beaver Damage Control document, provides helpful suggestions on how to control a chronic beaver or beaver dam issue on your property. If issues are developing at your dam due to beaver activity, always consult with your DNR Regional Water Management Engineer before implementing structural solutions as some activities will require review and approval (permit) prior to construction. Solutions for issues with the beaver themselves are addressed in the linked articles listed below.
General mitigation strategies for beaver control at man-made dams can be broken down into prevention and restoration categories. Examples of prevention might include wire or welded inlet guards, particular inlet design to dissuade beaver or trapping/other population control methods. Restoration activities might include burrow excavation and filling or debris removal at the principal or auxiliary spillways. In our next issue, we will outline beaver mitigation strategies at dams in more detail.
Helpful Sources and References
WDNR - Beaver Damage Control – Guidelines for People with Beaver Damage Problems:
This document overviews living with the problem of beaver; protecting your property; discouraging colonization; removal of dams, lodges, and beaver; legal definitions; laws for landowners and health notes.
Wisconsin Department of Natural Resources. Beaver Damage Control. Online at: https://dnr.wi.gov/topic/waterways/factsheets/beaverdamage.pdf
USDA – APHIS - Wildlife Services Cooperative Beaver Damage Management Program:
In the 80s, Wildlife Services cooperatively brought together interested parties to discuss severe beaver damage problems facing northern Wisconsin. This document provides an overview on how Wildlife Services has expanded beaver damage control to the whole coldwater ecosystem including, “road and culvert protection, wild rice habitat management, timber resource protection, preservation of sensitive habitats/plants, trail and trail bridge protection, protection of existing stream habitat improvement structures and protection of dams and impoundments.”
USDA-APHIS-Wildlife Services (2015). Cooperative Beaver Damage Management Program. Online at: https://www.aphis.usda.gov/aphis/ourfocus/wildlifedamage/operational-activities/sa_beavers/ct_wisconsin
USDA - How to Keep Beavers from Plugging Culverts:
This publication includes information on preventing beaver from damming culverts. It also includes more general methods for beaver control that can be applied to many different site locations.
United States Department of Agriculture. 2005. How to Keep Beavers from Plugging Culverts. 4E42C52-Beaver Proofing Culverts. Online at: https://www.fs.fed.us/t-d/pubs/pdfpubs/pdf05772830/pdf05772830dpi300.pdf
FEMA - Impacts of Animals on Earthen Dams:
This publication includes the effects of beaver on earthen dams and includes solutions on how to prevent or remediate beaver damages.
Federal Emergency Management Agency, 2005. Impacts of Animals on Earthen Dams. Technical Manual for Dam Owners No. 473. Online at: https://www.fema.gov/media-library/assets/documents/891
USFWS - The Beaver Restoration Guidebook: Working with Beaver to Restore Streams, Wetlands, and Floodplains:
This document provides a broad overview of beaver and mitigation strategies and studies that have been completed to help control them.
Pollock, M.M., G. Lewallen, K. Woodruff, C.E. Jordan and J.M. Castro (Editors) 2015. The Beaver Restoration Guidebook: Working with Beaver to Restore Streams, Wetlands, and Floodplains. Version 1.0. United States Fish and Wildlife Service, Portland, Oregon. 189 pp. Online at: http://www.fws.gov/oregonfwo/ToolsForLandowners/RiverScience/Beaver.asp
The DNR Dam Safety/Floodplain Management Program is pleased to announce that four regional water management engineers (WMEs) joined our team this spring! They will be based out of these DNR service centers:
Mike Stone - Fitchburg
Forrest Van Asten - Rhinelander
Megan Duffy – La Crosse
Hanna Johnson - Wisconsin Rapids
Regional WMEs are your local contacts for technical questions on dams and floodplain studies. These staff also assist with floodplain management. A complete list of the WMEs by county, including telephone numbers, email addresses and mailing addresses is available on the Dam Safety web page.
Mike Stone, Water Management Engineer, Fitchburg, WI
I grew up in Wausau, WI. I went to the University of Wisconsin-Madison and graduated in the spring of 2011 with a bachelor’s degree in Civil Engineering. I began my career out of college by working for Fickett Structural Solutions in Middleton, WI for almost three years. At Fickett, I was involved with Wisconsin Department of Transportation (WisDOT) sign inspections along with structural steel and welding fabrication and inspection for EPIC Systems in Verona, WI. I then went to work for Collins Engineers in Milwaukee and have been with them for the past six years. I was mainly involved with WisDOT projects which included some construction inspection of roadways and bridges and structural inspections of signs, culverts, walls, and bridges.
When I’m not at work I enjoy being with my friends and family in the great outdoors. My favorite activities include hunting and fishing and anything outside. I’ve been hunting since I was six years old and fishing since I was a baby. I always look forward to fall and hunting season, but I also love to go up north to my family’s cabin in Michigan’s Upper Peninsula, sharing my love of the outdoors with my wife and our 10-month-old daughter.
Forrest Van Asten, Water Management Engineer, Rhinelander, WI
I grew up in the Town of Suamico, just north of Green Bay, WI. I attended Michigan Technological University and graduated in 2007 with a degree in Civil Engineering. Upon graduating, I began working for WisDOT in highway design and construction out of their Green Bay office. In 2008, I married my wife Carolyn, who I had met at college. Later that year, we moved to her hometown of Tomahawk, and I was able to transfer to WisDOT’s Rhinelander office.
Since that time, I have continued to work in highway design and construction. However, in my college years, I emphasized in Water Resources related engineering classes, and was always hoping to someday work more specifically in that field. That is why I couldn’t pass up the opportunity to work for WDNR as a Water Management Engineer.
My wife and I continue to live in Tomahawk. We have three children, ages 5, 8, and 9. We live on the Wisconsin River in Tomahawk, and enjoy fishing, boating, skiing, and kayaking. I also own a deer camp in Escanaba, MI with my dad and brother. If I’m not deer hunting in the U.P., I’m usually fishing, hiking, or camping up there. I consider it my second home, even though my Yooper friends might disagree (since I wasn’t born there).
Megan Duffy, Water Management Engineer, La Crosse, WI
I just graduated from UW-Madison in December 2019 with a degree in Biological Systems Engineering. I just joined the DNR as a Water Management Engineer and am very excited about the opportunity to work for such a great department. I'm from the Milwaukee area, but I look forward to moving to La Crosse and being able to explore the area and all of the outdoor activities that are available there. In my free time I like to relax with hiking and painting, but I'm always looking for new activities to try.
Hanna Johnson, Water Management Engineer, Wisconsin Rapids, WI
I’m Hanna Johnson, my husband, Aaron and I live in rural Juneau County with our dog, 2 horses, 2 cats and 8 chickens. We love being outdoors and enjoy many outdoor activities: hiking/walking, hunting, fishing, horseback riding, gardening, wild foraging, etc.
I graduated from UW-Madison in May 2011 with my B.S. in Civil and Environmental Engineering with the Environmental Option and a certificate in Environmental Studies. I served as a Project Engineer/Leader for WisDOT in the Project Development Section for just over 6 years. I then went to work for CEP Engineering, LLC as a Project Manager where I continued to work on WisDOT projects, along with county bridge inspections and DOA projects. I have worked for CEP for just over 2 years.
I am thrilled to start my new position with the DNR!