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Coastal Hazards

CRMC Policy Relating to Coastal Hazards

The Coastal Resources Management Program (CRMP) has developed regulations for reconstruction after "the big one" as well as other severe storms (Section 180. Emergency Assents). More important are the regulations that are designed to minimize the impact of coastal hazards. Policies regulating where to build on a vulnerable property (Section 140. Setbacks), construction of shoreline protection facilities (various sections), and beneficial reuse of dredged materials help to mitigate some of the hazards associated with coastal living. Sea level rise is a hazard that is only indirectly addressed in the CRMP. Erosion setbacks are very effective regulations that protect the homeowner and the public resources. Much of the Rhode Island shoreline is eroding. Erosion rates are calculated by comparing the shoreline location from historic aerial photographs to the most recent shoreline position. Sections of the south shore barriers have erosion rates of more than three feet per year. That is an average rate over time. In reality, the shoreline may erode tens of feet in a single storm, followed by some accretion. In critical erosion areas on barriers, all residential construction with less than six units must be set back 30 times and commercial property 60 times the average annual erosion rate. The farther the house or commercial structure is setback from the shore, the longer it will last. Unfortunately, these regulations were enacted about thirty years ago. The Council may want to consider policy for when the setback is gone and the structure is on the active beach (figure 1).

Figure 1. House pilings in the wave swash. Old pilings and ISDS exposed after a storm.

Impacts of storm erosion on ISDS are a potential public health problem (figure 2). CRMC worked with RIDEM to develop regulations for repairs to ISDS in critical erosion areas (ISDS Repair Guidance in Critical Erosion Areas, January 31, 2006).

Figure 2. ISDS exposed by storm surge and waves.

Shoreline Protection Structures are prohibited along Type 1 shorelines except where they are used to protect historic structures that are listed on the National Register of Historic Places (Section 220). There are several reasons for this prohibition. The structures reflect wave energy, often causing erosion around the sides of the structure and can cause scouring seaward of the structure. In addition, the structures disrupt sediment transport, both by sequestering sediment that would normally erode from a bank or dune to form new beaches (figure 3), and by physically blocking the sand movement along the shoreline (figure 4). Shoreline protection structures often impact lateral public access along the shoreline. In other words, these structures help protect the property where they are built, but often harm adjacent properties. They are a contributing factor in the narrowing and loss of beaches, and they inhibit the public's right to lateral shoreline access (figure 5). Many of the structures that were built prior to the CRMP cannot withstand moderate storms (figure 6).

Figure 3. Sediment that erodes from the headland bluffs forms the beaches. The dotted line marks the extent of the slump block before the sediment was transported by waves and currents.

Figure 4. The jetty interrupts the longshore sand transport.

Figure 5. Lateral access is limited to low tide.

Figure 6. Many shoreline protection structures cannot withstand moderate storm energy.

CRMC advocates the beneficial reuse of dredged material. The South Coast Habitat Restoration Project is an example of beneficial reuse that has created wider beaches and has the secondary benefit of providing protection for some coastal properties (figure 7).

Figure 7. Beach with dredged sand on the left shows no erosional scarp. The beach on the right shows dune scarp and newly exposed ISDS.

Historical Perspective

The following lists the relevant sections of the CRMP dealing with coastal hazards.

Post Storm Actions:
Section 180. Emergency Assents

Pre Storm Mitigation:
Section 140. Setbacks

Section 210.1. Coastal Beaches

Policy

C.1. The Council's goals are (a) to preserve the qualities of, and public access to those beaches which are an important recreational resource (adjacent to Type 1 and 2 waters); (b) to prevent activities that will significantly disrupt longshore and/or onshore-offshore beach processes, thereby creating an erosion or flooding hazard; and, (c) to prevent construction in high hazard areas; and, (d) to protect the scenic and ecologic value of beaches.

Prohibitions

D.1.The construction of new structures other than accessways, walkover structures, and beach facilities, are prohibited in setback areas.

Section 210.2. Barrier Islands and Spits

Policy

C.1 On barriers classified as undeveloped in Table 4, the Council's goal is to preserve, protect, and where possible, restore these features as conservation areas and as buffers that protect salt ponds and the mainland from storms and hurricanes.

C.2. On barriers classified as developed in Table 4, the Council's goal is to ensure that the risks of storm damage and erosion for the people inhabiting these features are minimized, that activities that may reduce the effectiveness of the barrier as a storm buffer are avoided, and that associated wetlands and ponds are protected.

C.5. The Council recognizes the highly dynamic nature of barriers and that storms may cause sudden and significant changes to the geomorphic form of these coastal features. Accordingly, large scale public infrastructure improvements and dense development is inappropriate. Therefore, the construction or expansion of new infrastructure or utilities shall be prohibited on all barriers including water, gas and sewer lines. It is not the intention of these policies to apply to individual, on-site water supply systems or individual sewage disposal systems, or gas lines. The use of plastic snow-fencing on all barriers is prohibited.

C.6 It is the Council's policy to assure that all construction permitted on developed barriers is undertaken to provide for the greatest physical security of the inhabitants of the barrier and adjoining mainland and to maintain, to as great an extent as possible, the qualities of the adjacent coastal pond and wetlands. (See detailed regulations for construction on dunes and beaches in Section 210.1, flood hazard areas in Section 300.3, and other applicable policies and standards in the Coastal Resources Management Program and special area management plans). The construction of new buildings is prohibited on developed barriers on which only roads, utility lines, and other forms of public infrastructure were present as of 1985.

C.7. With the exception of boardwalks and snow fencing utilized to trap sand, all residential and non-water-dependent recreational, commercial, and industrial structures on undeveloped barriers physically destroyed 50 percent or more by storm-induced flooding, wave or wind damage may not be reconstructed regardless of the insurance coverage carried.

Prohibitions

D.4. Alterations to undeveloped barriers are prohibited except where the primary purpose of the project is protection, maintenance, restoration or improvement of the feature as a natural habitat for native plants and wildlife. In no case shall structural shoreline protection facilities be used to preserve or enhance these areas as a natural habitat or to protect the shoreline feature.

D.5 The construction or expansion of new infrastructure or utilities shall be prohibited on all barriers including water, gas and sewer lines. It is not the intention of these policies to apply to individual, on-site water supply systems or individual sewage disposal systems, or gas lines.

D.6. New development is prohibited on moderately developed barriers except where the primary purpose of the project is restoration, protection, or improvement of the feature as a natural habitat for plants and wildlife or as allowed under Section 210.3.C.3 herein. In no case shall structural shoreline protection facilities be used to preserve or enhance these areas as a natural habitat or to protect the shoreline feature.

D.7. The construction of new buildings is prohibited on developed barriers on which only roads, utility lines, and other forms of public infrastructure were present as of 1985.

D.8. All residential construction shall be setback a minimum of 50 feet. Residential construction is prohibited in the setback zone. A special exception shall be required for relief from the 50 foot setback requirement on barriers unless the activity proposed is a beach facility or walkover structure in which case a variance from the setback provisions shall be required. A variance shall be required for relief from the setback requirement on barriers for the area that lies between the 50 foot minimum setback and any greater setback based on the annual erosion rate. No new Individual Sewage Disposal Systems shall be constructed within the 50 foot setback area (see Section 300.6.A.2 for definition of new ISDS). Walkover structures may be permitted over the dunes in order to gain access to the beach.

Section 210.4. Coastal Headlands, Bluffs and Cliffs

Policy

C.1 The Council's goals are to (a) protect coastal cliffs, and bluffs from activities and alterations that may damage the value of these features as sources of sediment to beaches and as a buffer against storm waves and flooding; (b) prevent any construction in contiguous areas that may weaken the feature and has the potential of creating a hazard; and (c) preserve the scenic and ecological values of these features.

C.3 On shorelines adjacent to Type 1 waters, the Council shall prohibit construction on or alteration of coastal cliffs and bluffs and contiguous areas where such construction or alteration has a reasonable probability of causing or accelerating erosion or degrading a generally recognized scenic vista. The Council shall require suitable unaltered buffer zones on cliffs and bluffs where erosion or substrate stability can be affected by facility construction or use. In determining whether a reasonable probability exists that increased erosion or loss of scenic values will result from the proposed construction or alteration, the Council shall consider the following:

1. the exposure of the feature to the erosional forces of tidal currents, storm waves and storm-surge flooding, wind and surface runoff, and other such natural processes;
2. the composition of the feature involved as well as its slope, stratigraphy, height, exposure, and vegetative cover;
3. existing types and levels of use and alteration;
4. competent geological evidence to evaluate whether natural erosion of the feature in question is a significant source of sediments to nearby headland and barrier beaches and whether the proposed construction of alteration will substantially reduce that source of sediment; and
5. inclusion of the feature on an accepted inventory of significant scenic or natural areas or evidence of public use and enjoyment as a scenic or natural area.

C.4 The Council shall encourage the use of non-structural methods to diminish frontal erosion associated with coastal cliffs and bluffs adjacent to Type 1 and Type 2 waters.

C.5 Construction or alterations to coastal cliff and bluffs contiguous to Type 2, 3, 4, 5 and 6 waters may be permitted if (a) the construction is undertaken to accommodate a designated priority use for the abutting water area, (b) the applicant has examined all reasonable alternatives and the Council has determined that the selected alternative is the most reasonable, and (c) only the minimum alteration necessary to support the designated priority use is made. In considering applications for permits for erosion-control measures, the Council shall weigh the impact of the proposed structure on the supply of sediments to nearby beaches. Where the Council finds that a substantial reduction or elimination of sediment is likely to result, and that natural erosional processes affecting the nearby beach will thereby be accelerated, it shall deny an application for Assent.

Section 210.7. Dunes

Findings

B.5. Individual Sewage Disposal Systems have the potential to become buoyant or be damaged during a severe storm event causing raw sewage to spill onto the beach. Therefore, no new Individual Sewage Disposal Systems should be constructed within the setback area. Repairs should, whenever possible, be located outside of the setback area.

Policy

C.1. The Council's goals are to: (a) protect the foredune zone from activities that have a potential to increase wind or wave erosion; (b) to prevent construction in high hazard areas and protect the public from dangerous storm forces; (c) to enhance the ability of dunes to serve as a natural storm buffer; and, (d) to protect the scenic and ecologic value of the foredune zone and dunes.

C.2. All residential construction shall be setback not less than 30 times the annual erosion rate and commercial construction shall be setback not less than 60 times the annual erosion rate. In no case shall the dune setbacks be less than 50 feet. All dune setbacks shall be measured from the landward edge of the foredune zone defined to be 25 feet landward of the dune crest. A special exception shall be required for relief from the 50 foot setback requirements from dunes and beaches on barriers unless the activity proposed is a beach facility or walkover structure in which case a variance from the dune setback provisions shall be required. A variance shall be required for relief from the setback requirements from dunes and beaches on barriers for the area that lies between the 50 foot minimum setback and any greater setback based on the annual erosion rate. No new Individual Sewage Disposal Systems shall be constructed within the 50 foot setback area from the dune or beaches or seaward of construction lines (see Section 300.6.A.2 for definition of new ISDS). Walkover structures may be permitted over the dunes in order to gain access to the beach.

C.3. Alteration of the foredune zone adjacent to Type 1 and 2 waters is prohibited except where the primary purpose of the project is non-structural protection, restoration, nourishment, or improvement of the feature as a natural habitat for native plants and wildlife. In no case shall structural shoreline protection facilities be used to preserve or enhance these areas as a natural habitat or to protect the shoreline feature. The Council may also permit the establishment of accessways (e.g., dune walkover structures) on foredunes provided that all requirements of this section are met.

Prohibitions

D.2. Alteration of the foredune zone adjacent to Type 1 and 2 waters is prohibited except where the primary purpose of the project is non-structural protection, restoration, nourishment, or improvement of the feature as a natural habitat for native plants and wildlife. In no case shall structural shoreline protection facilities be used to preserve or enhance these areas as a natural habitat or to protect the shoreline feature.

D.3. No new Individual Sewage Disposal Systems shall be constructed within the 50 foot setback area from the dune or beaches or seaward of construction lines (see Section 300.6.A.2 for definition of new ISDS).

Section 300.7. Construction of Shoreline Protection Facilities.

Policy

B.1 The Council favors non-structural methods for controlling erosion such as stabilization with vegetation and beach nourishment.

B.3 When structural shoreline protection is proposed, the Council shall require that the owner exhaust all reasonable and practical alternatives including, but not limited to, the relocation of the structure and nonstructural shoreline protection methods (see Section 300.7.E.1).

Prohibitions

D.1 The Council shall prohibit new structural shoreline protection methods on barriers classified as undeveloped, moderately developed, and developed and in Type 1 waters.

D.2 The Council shall prohibit the use of limited applications of riprap to protect structures ancillary to the primary structure.

D.3 Filling on a coastal feature or tidal waters beyond that which is consistent with 300.7.F.1 is prohibited.

D.4 Structural shoreline protection facilities are prohibited when proposed to be used to regain property lost through historical erosion or storm events. Additional Category B Requirements

E.1 Applicants for structural shoreline protection measures to control erosion shall, on the basis of sound professional information, demonstrate in writing all of the following:

1. an erosion hazard exists due to natural erosion processes and the proposed structure has a reasonable probability of controlling this erosion problem;
2. nonstructural shoreline protection has not worked in the past or will not work in the future because these methods are not suitable for the present site conditions;
3. there are no practical or reasonable alternatives to the proposed activity such as the relocation of structures that mitigate the need for structural shoreline protection;
4. the proposed structure is not likely to increase erosion in adjacent areas;
5. the proposed structure is an appropriate solution to the erosion problem considering such things as the long term erosion rate in the area, the likely effects of storms and hurricanes, and the stability of the shoreline on either side of the project;
6. describe the long-term maintenance program for the facility including financial commitments to pay for said maintenance; and, (g) new breakwaters, jetties, bulkheads, revetments, and seawalls shall be designed and certified by a registered professional engineer

Section 300.9. Dredging and Dredged Materials Disposal

Standards

F.5. Disposal for beach nourishment:

1. The placement of dredged materials on a beach is a preferred disposal alternative, providing that the materials in question are predominantly clean sands possessing grain size and such other characteristics to make them compatible with the naturally occurring beach material.
2. In areas where the processes of littoral drift would result in significant re-entry of dredged sediments into a navigable waterway, dredged materials must be placed on the downdrift side of the inlet.
3. All applicable requirements of Section 300.2 shall be met.