Water Column Spring 02

n Seawalls and Your Lake An eroding shoreline can be a big headache for lakeshore homeowners. After all, you’ve spent a premium for your lakefront property and you’d like to keep it in place. What can you do? More importantly, what can you do without adversely affecting your lake and your property value? The objective of lake shoreline protection techniques is to stabilize and protect these land forms against scour and erosion from forces such as wave action, ice action, seepage, and runoff from upland areas. Shoreline stabilization methods fall into two broad areas: 1. nonstructural (vegetation) 2. structural a. flexible (rip-rap, glacial stone) b. rigid (seawalls) Vegetation Vegetation effectively controls runoff erosion on slopes or banks leading down to the water; however, it is less effective against direct wave action or seepage-caused bank slumping. Grasses are effective on slopes flatter than 3:1 (three feet horizontal run for each one foot vertical rise). On steeper slopes, deep-rooted grasses, woody shrubs, or trees are more effective. Bioengineered materials (erosion control mats, biologs, etc.) may be used to stabilize slopes while the vegetation is becoming established. Benefits of a vegetated shoreline are numerous and include: • Great habitat for aquatic organisms that live on the edge •A barrier to Canada geese (they won’t walk through tall grass, shrubs, Fall 2003 or other dense vegetation) • Shade, which discourages dense growth of aquatic plants (such as Vol. 15, No. 3 Eurasian watermilfoil) along the lakeshore. Flexible Structures Rip-rap (preferably with natural, glacial stone), when properly installed, provides effective, long-term shoreline protection from waves, ice action, and bank slumping caused by seepage. Unfortunately, such structures are seldom installed properly but we’ll address this in a future issue of WaterColumn. A glacial stone revetment is Natural vegetation can protect even steep lakeshore slopes. “flexible” because waves move the stones slightly and flow over and into spaces between the stones, which dissipate the ater Colum erosive energy of the waves. An additional ecological advantage of glacial stone is that aquatic insects (food for young fish) find shelter between the stones and rooted plants can grow within the stones, providing a more natural appearance. Clean Lakes Program • Office of Water Quality • Indiana Department of Environmental Management W many ecological problems for lakes. 1. Reflected wave energy scours the reflection lakebed along the seawall, and dissipation seawall waves with it, scours rooted plants waves important as habitat for fish, aquatic insects (fish food), and refuge amphibians. scour 2. Wave scouring also resuspends sediments, increasing turbidity in the lake. Glacial stone rip-rap dissipates wave 3. Wave scouring stirs up sediment Seawalls reflect waves, which scours out energy and is habitat for many aquatic the lake sediments. organisms. phosphorus, increasing algae growth. 4. Seawalls are a barrier for frogs Seawalls leaving the water after breeding. that drew them to the water in the Seawalls are rigid structures They can’t get out and may first place. This is seen in declining that do not move when waves actually drown. property values. For example, a strike them. Wave energy instead is study in Maine has shown that a reflected back into the lake and To prove the ecological value of three-foot decrease in Secchi disk down along the shore. They are glacial stone vs. seawalls, 17 transparency (water clarity) used where steep banks prohibit cooperative lakefront landowners dropped the average selling price of the forms of protection suitable on on Lake Wawasee refaced 1,000 homes by $7,500 - $14,000 per 100 shallow slopes. The seawall is feet of seawalls with glacial stone. feet of lakefront property. A 2002 placed vertically in soils and forms One-year results showed fish study in Minnesota came to similar a barrier between the land surface diversity increased by 36%, rooted conclusions. A three-foot decrease in and the water. The seawall itself plants present at 81% of the sites, water clarity on Leech Lake can be constructed of sheet pile, and aquatic insect diversity and dropped property values by $594 wood, or concrete. Proper seawall abundance were doubled at the per foot of frontage. A three-foot construction requires: (a) refaced sites. improvement in clarity increased anchoring either by driving the Economic values also become property values by $423 per foot of pile deep into the ground or the important when considering frontage. Therefore, building a placement of “deadman” anchors shoreline management. People are seawall may not be the best way to and (b) protecting the “toe” of the willing to pay a premium price for maintain your property’s value. seawall with large stones to prevent lakefront property because of the undercutting. Seawalls not properly benefits of living on the lake. These What Does This Mean for constructed may quickly begin benefits include the scenic beauty, Lakeshore Homeowners? leaning toward the water due to peacefulness, swimming, fishing, You’ve paid a premium price back-pressure. watching birds, and others. But for your lakefront property. If your While many lakeshore installing seawalls is an action of shoreline is eroding, of course you homeowners apparently appreciate lakefront homeowners that need to fix it. However, before you the looks of seawalls, they pose actually degrades the very qualities do anything, you should first have Concrete seawall Proper construction of a seawall Wooden seawall Fill Cap Original Sheet pile ground surface Wale Tie-back Anchor (deadman) 2 a comprehensive evaluation of the includes information on the health It is important to note that a cause of the problem. Once the risks and health benefits of eating fish advisory on a body of water cause is determined, work with fish and the proper cleaning and does not necessarily mean that the your lake management professional preparation of fish. This water is unsafe for other to select the best corrective action publication is available annually recreational activities. If the water for the problem . one that also through cooperative efforts posed a hazard to human health, has the minimum impact on the between the Indiana State there would be a separate advisory lake. Seawalls should only be used Department of Health, the Indiana issued for recreational activities like when the eroding lakeshore is Department of Environmental swimming or skiing. Requests for a steep, with high banks, and high Management, the Department of free copy of the 2003 Indiana Fish wave energy. You don’t need a Natural Resources, and Purdue Consumption Advisory and seawall to repair minor erosion or University. questions about eating sport- in low wave energy situations and, “We have tried to include caught fish can be directed to the in fact, you may actually do more everything a person might want to Indiana State Department of damage to your lake than good. know about eating sport-caught Health, at (317) 233-7055. For more information, contact fish in Indiana,” said LaNetta Information from the 2003 Fish your county Natural Resources Alexander, environmental Consumption Advisory is available Conservation Service, an agency epidemiologist at the Indiana State on the Web in two ways: by body within the U.S. Department of Department of Health. “The of water and by county (from a Agriculture. They have technical advisory is designed to provide Web site prepared by Purdue manuals and expertise to advise people with guidelines on how University). Both versions are you on proper lakeshore erosion much and how often they should available at http://www.IN.gov/ control. You may also contact the eat the fish,” Alexander said. “By isdh (click on “Data and Indiana DNR, Division of Soil following the advisory and eating Statistics”). Other available Web Conservation; Web site: http:// fish in moderation, you help avoid resources include: www.ai.org/dnr/soilcons/. the risk of accumulating •mercury information, at http:// contaminants in your body over www.in.gov/idem/mercury/ Sources of Information time and gain the benefits of a •a mercury fact sheet, at http:// Used in this Article protein source that’s low in www.in.gov/idem/mercury/ McComas, S., D. Jansen, J. Marter, saturated fats.” prevention/mercfact.pdf and D. Roseboom. 1986. The advisory is not meant to •a polychlorinated biphenyls Shoreline protection. Lake and discourage fishing, but rather to (PCBs) fact sheet, at http:// Reservoir Management, Vol. maximize the benefits and www.in.gov/idem/macs/ 2:421-425. minimize the risk of eating Indiana factsheets/media/pcbs.html McComas, S. 2003. Lake and Pond fish, she said. The fish advisories Management Guidebook. Lewis are based on fish tissue sampled by Publishers, Boca Raton. the Department of Environmental IDNR. 1997. Lakeshore Protection Management; the agency gathers in Indiana. Lake and River data on fish during its annual Enhancement Program, Division watershed assessment sampling. of Soil Conservation, Mercury and polychlorinated Indianapolis. Available online at: biphenyls (PCBs) are the major WATER COLUMN http://www.ai.org/dnr/soilcons/ contaminants that can be present Published quarterly pdfs/seawall.pdf. in the tissues of Indiana fish, by the Indiana Clean Lakes Program although pesticides and heavy as a medium for open exchange of metals can also be present. information regarding lake and State Issues 2003 “The Fish Consumption watershed management in Indiana Advisory is a tool everyone who William W. Jones, Editor Indiana Fish eats fish caught from Indiana waters should familiarize Address all correspondence to: Consumption Advisory themselves with,” said Department SPEA 347 of Environmental Management 1315 E. Tenth Street The Indiana State Department of Indiana University Health has issued the 2003 Indiana Commissioner Lori F. Kaplan. “By Bloomington, IN 47405-1701 Fish Consumption Advisory—both putting this critical information in E-mail: [email protected] in print and on its Web site.

Load more