Stabilize bluffs and rocky shores with rip-rap

The natural movement of the tides and severe to moderate storms with wave surge at high tide can cause the erosion of upland soils at the edge of the coastal bluff. Placing rip-rap (angular stone in various sizes usually larger than two feet diameter) can stabilize the base of an eroding bluff and slow erosion in some cases. The rip-rap must be placed on a bed of crushed stone or geotextile fabric to fully protect the soils underneath, and be installed at the angle of the existing bluff or no steeper than a 2:1 slope. The slope of the installation is critical, as it will allow the rip-rap to blend with the natural shoreline and absorb wave energy. Pack stones densely to prevent wave action from pulling erodible soils out of the bluff through the stones. The height of the rip-rap should be limited to no greater than twice the maximum wave height for the affected area. Rip-rap is most effective when placed in areas that are likely to be under heavy wave stress. Areas on the bluff that are above wave action can, in most cases, be stabilized with a combination of other techniques. Often, vegetation is used in conjunction with rip-rap to improve its overall effectiveness.

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. This step is critical for bluffs that are exhibiting signs of groundwater discharge through the bluff face. In some cases, even properly installed rip-rap can restrict the natural movement of groundwater, potentially causing super saturation of the soil and catastrophic slope failure or a landslide.

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. The plan does not need to be prepared by a professional in all cases; however, a good, clear plan can improve the efficiency and timeliness of any permitting that may be required. Good plans also will be beneficial to the construction contractor and can help avoid costly mistakes during the construction process.

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. Replacing existing rip-rap usually qualifies for permit-by-rule; however, installing new rip-rap does not, and an individual permit may 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.