Runoff from upland areas (both on and below the land surface) can cause coastal erosion. Changes to the landscape due to changes in land use over time can change runoff patterns and/or increase the amount of water that is moving through the area, again contributing to added stress on the shoreline. Drainage, consequently, is a key factor in bluff stability. Actions that increase surface and subsurface water flow to a coastal bluff, such as ditching, construction of new impervious area (roofs, roads/driveways, paths, etc.), changes to natural grading, and removal of or changes to vegetation, can contribute to destabilization of the coastal bluff and cause soil erosion. Saturated soils add weight to coastal bluffs and can weaken stability, contributing to increased risk of slumping or landslides.
When surface water collected by roofs, driveways, paths, and lawns flows toward and down the bluff face, erosion can accelerate over time or in some cases the bluff can collapse. Walkways down the face of a bluff can also concentrate surface water flow and contribute to bluff instability. Drainage may be a contributing factor to coastal erosion even when signs of surface erosion are not evident due to the presence of subsurface water within the soil profile. Seepage of water out of the bluff face, in addition to surface erosion due to runoff and wave action, can often be a large contributor to coastal bluff erosion.
Addressing drainage issues requires a detailed understanding of the root causes of the water issues, as well as the soil conditions on the site. In most cases, Best Management Practices (BMPs) can be applied to mitigate or improve drainage. The Maine Erosion and Sediment Control BMP Manualprovides a detailed description of the recommended structural and non-structural methods to mitigate erosion. The best solution for a given drainage issue may involve the construction of one or a combination of BMPs, such as curtain drains, catch basins, open and closed ditches, french drains, dry wells, etc.
Follow the steps below to gain the environmental and regulatory information needed for decision making. The steps are listed in general order, although some steps may be conducted concurrently.
1) Contact local, state and/or federal officials to obtain regulatory advice. Individuals experienced with coastal regulations may not need to seek regulatory advice in all cases; however, if in doubt seek advice before proceeding with a project.
2) Obtain an assessment from a certified engineer, landscape architect, or other qualified environmental professional. In most cases, local, state, and/or federal regulators can help identify the best professional discipline to assist with a specific project.
3) Owners of coastal property along eroding bluffs or near landslide-prone areas should check their insurance coverage to make sure they have adequate liability coverage related to loss due to landslides or shoreline erosion, as well as flood insurance.
4) If implementation of one or more Best Management Practices (BMPs) is recommended, develop an erosion mitigation plan.
5) Be neighborly. If the plan involves work at or near a property boundary, consider sharing the plan with the abutter(s) to make sure they fully understand the work to be performed and the potential impact to drainage on their property. This consultation is a courtesy at this stage, and not a regulatory mandate, however obtaining “buy in” from abutter(s) can potentially avoid neighbor disputes that lead to costly permitting and/or construction delays.
6) Share plans with local code enforcement to determine what, if any, local ordinances apply. Local Shoreland Zoning requirements will determine the acceptable location for structures such as drainage features, catch basins, roads/driveways, paths, etc.
7) If the plan involves alterations within 75 feet of highest annual tide (HAT), within or adjacent to another protected natural resource as defined by the Maine Natural Resources Protection Act (NRPA), or within a development permitted by the Site Location of Development Act (Site Law), a permit will likely be required.
8) If the plan involves work below the HAT, and/or in a freshwater wetland or habitat for endangered or threatened species, a federal permit under the Federal Clean Water Act and Rivers and Harbors Act may be required. Share the plan with all applicable federal authorities to determine which permits may be necessary.
9) It is good general practice to hire contractors that are experienced with coastal stabilization projects and the implementation of Best Management Practices.