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Nature's Flood Control

September 2008 was the wettest on record in Southern Maine (as much as 15 inches on the coast, or 9.3 billion gallons in Kennebunk alone!) supporting many climate scientists predictions that annual rainfall amounts will increase as a result of global climate change.  And last spring the snow pack was in the top 25% of historic levels, holding some 4-10 inches of water.  The effects of increased rain amounts can be seen in road side wash outs and flooded basements, as well as murky waters along our beaches.  Solutions to these water problems typically range from armoring road shoulders with piles of rock or installing sump pumps, even putting houses on stilts.  But a cheaper and more beautiful solution sits right in our backyards.

Swamps, bogs, saltmarshes, heaths, peat lands, fens, and vernal pools; these are all wetlands.  Wetlands have long been thought of as having little value, primarily just a source of biting insects with little use for development.  But wetlands provide much greater benefits in the service of flood control.  In inland areas wetlands receive runoff and direct rainfall and retain that water temporarily to be released slowly over time.  The EPA estimates that 1 acre of wetlands can store 1 million gallons of water.  Wetlands along rivers provide pathways for increased water levels and slow down flow rates, reducing erosion and absorbing flood waters. Along the coast, marshes absorb and disperse the energy of incoming storm surges.  This service is provided at no cost and requires no maintenance.  Pretty good deal.

Unfortunately, we are losing our wetlands to a number of influences.  Slowly but surely the increasing demand for houses and roads is taking its toll on the landscape.  By 1980 Maine had already lost 20% of its wetlands to farmland and development.  The amount of land developed in Maine between 1970 and 1990 was as much as in the whole history leading up to that point, and the State Planning Office estimates that the rate of development in Maine will double by 2010.  In addition, the population in York County has more than doubled in the last 50 years.

In addition to loss from direct human use, wetland loss will be driven by climate change.  As sea level rises, coastal wetlands will become flooded and eventually submerged permanently.  Conservative predictions place sea level rise in the next century between 7 and 23 inches.  With these systems gone coastal communities will be more susceptible to flood events like the ones on Mothers Day in 2006 and Patriots Day in 2007. 

The effects of these changes are being felt in areas downstream when large rain events swell our rivers and they over top their banks.  Without enough upstream storage, the rain flows off the landscape and quickly spreads out into the floodplains along rivers and streams, and quite often into someone’s backyard. 

The costs associated with flooding aren’t small.   The Town of Kennebunk spent $375,000 to relocate or elevate flooded homes along the Mousam River, with FEMA contributing $1,125,000.  The Mothers Day Storm damage was estimated at around $7.5 million.  The costs of flooding have had farther reaching consequences with insurance companies reducing coverage for storm damage or simply canceling policies all together.  The State Planning Office estimates that 75% of homes in flood plains are not insured.

The value of Maine’s 5 million acres of wetlands has been calculated (by the Clean Water Network) at around $31 billion for the services they provide which, aside from flood mitigation, include fish and bird habitat, water treatment, ground water recharge, and scenic and recreational opportunities. 

A number of legislative acts provide protections for wetlands, most notably the Federal Clean Water Act of 1972 championed by our own Senator Edmund Muskie.  At the state level the Maine Natural Resource Protection Act regulates moving of earth in and around wetlands and Maine Shoreland Zoning laws regulate land use within the area surrounding wetlands.  The effectiveness of these laws however is often limited by lack of enforcement due to shortages of funding and manpower. 

Sometimes wetland loss is permitted.  Work on roads and bridges often involves the filling of portions of wetlands.  The law requires these losses to be compensated for by the creation of new wetlands or wetland restoration.  The replacements usually take the form of engineered drainage swales and retention ponds.  Unfortunately these are often not an adequate substitute for the original system.  An Army Corps of Engineers study found that only 17% percent of wetland mitigation sites functioned as adequate replacements.  The substitute wetlands may be in a completely different location and the ecology may be dramatically different.

So what is to be done?  Numerous organizations are hard at work to address these issues.  Municipalities are constantly updating there zoning ordinances and incorporating new techniques for stormwater management.  People are becoming more aware of the risks of living in areas prone to flooding as we have seen on a large scale in the Midwestern and Gulf Coast states.  The fact is that it’s just plain good economic sense to preserve our ‘green infrastructure’. Wetlands provide services that we can no longer afford to take for granted. 

This view has recently been supported by the National Marine Fisheries Service which recently called for a moratorium on development in the flood plains around Puget Sound, Washington.  There elevated levels of pollutants in stormwater are damaging populations of endangered Chinook salmon and Orcas.

The solution to the problem of wetland loss is relatively straight forward, but requires the willpower of all of us to succeed.  Landowners can help by voluntarily limiting activities around wetlands.  If your land borders a wetland, think about not mowing right to the waters edge.  Instead, consider leaving a wide buffer of trees and vegetation that will help reduce the impacts of flooding and runoff.  Rain barrels and rain gardens can be used to capture rainwater from your roof and parking area.  You can even allow a part of your yard to grow into a natural meadow full of wildflowers which will attract songbirds and wildlife.  If each of us can help restore the natural landscape the result will be savings to our communities and benefits to public health and the environment.

The Wells National Estuarine Research Reserve at Laudholm Farm, Wells, Maine Copyright 2006 All rights reserved. Collaboration with NOAA CSC, Charleston SC