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The current study has identified certain morphologic trends along the Saco Bay shoreline. Net erosion and accretion, and subsequent subaerial-to-intertidal beach volumetric changes were determined at 100-foot beach profile transects along the shoreline. Certain beach features, such as maximum dune elevation, are important safety features in protecting developed shorelines from storm events. As a result, shorefront communities may find portions of this document useful for planning purposes. The following recommendations are solely based on trends seen within the current study. It is suggested that communities use this document for preliminary guidance only, and contact appropriate consultants in order to receive additional guidance regarding shoreline studies and subsequent planning. It is also recommended that communities along Saco Bay work to develop federally approved hazard mitigation plans in order to deal with both short and long-term coastal hazards. Recommendations include the following:
Regional Sediment Management
Communities within the Saco Bay littoral cell should consider implementation of a regional sediment management plan. Sediment, in general, originates from and is confined within the bay. Sand "recycling" may therefore be an extremely effective measure in dealing with areas of erosion and accretion. Previous authors (e.g., Kelley and others, 1995) have proposed such a sediment management plan. Since there are two federal navigation projects located at both ends of the bay (one at the source, the Saco River; and one at Scarborough River), communities should look to couple their efforts with federal dredging projects (under Corps Operations and Management funding) for sediment backpassing from northern, highly accretive beaches, to southern erosive beaches. Saco Bay seems to be a perfect location to implement the Corps' new Regional Sediment Management (RSM) program, and funding may be available through this program (Rosati and others, 2001).
Elevating Above Base Flood Elevations
Communities exhibiting maximum profile elevations (e.g., dune or seawall crests) below established FEMA base flood elevations should take mitigation actions to create more protective frontal dunes, or in the case of existing rocky shoreline outcrops, elevating existing structures above the base flood elevation (BFE). This should be applicable even to those areas that have a relatively wide landward distance to structure. Sections of shoreline that should consider this recommendation are:
Widening Dry Beach Widths
Communities exhibiting dry beach widths less than 25 ft should consider some form of beach restoration (especially those stretches of shoreline that have dry beach widths of less than 25 ft and total landward distances of less than 100 ft). Sections of shoreline that should consider this recommendation are:
Increasing Total Landward Widths
Communities with total landward widths from HWL to the seaward edge of the first habitable structure of approximately 100 ft or less should consider some form of beach and/or dune restoration in order to provide a larger natural buffer between dunes or seawalls and habitable structures. This recommendation does not apply to habitable structures fronted by exposed rocky shorelines (e.g., southern Hills Beach). Sections of shoreline that should consider this recommendation are:
Plan for 100-yr Erosion
Communities with projected 100-year shorelines showing areas of erosion that may adversely affect habitable structures should consider advance beach restoration and/or structure relocation or acquisition measures. Sections of shoreline that should consider this recommendation are:
Plan for 100-yr Accretion
Communities with projected 100-year shorelines showing areas of substantial potential accretion must plan accordingly. As shorelines build seaward, community planners should be prepared to address ownership, access, zoning, and development issues that may result. Sections of shoreline that should consider this recommendation are:
Consider Shoreline Structure Maintenance or Removal
Communities with existing seawalls should evaluate the effectiveness of the structures in protecting development, the future rehabilitation/renovation expenses associated with structure maintenance, and investigate additional shoreline protection options. Sections of shoreline that should consider this recommendation are:
Proximity to Tidal Inlets
Communities with areas situated within or directly adjacent to the limits of a tidal inlet should pay close attention to historical and existing erosion trends, as such areas are generally erosive 'hotspots,' are generally lower in elevation, and are subsequently prone to periodic overwash. Sections of shoreline that should consider this recommendation are:
Section 111 Plan Alternatives: Coastal Engineering and Mitigation at Camp Ellis
Based on the analysis in this report, erosion problems along the Saco Bay shoreline appear to be localized to Camp Ellis Beach and portions of Ferry Beach, and also appear to be a direct result of the negative influence of the Saco River jetties. Upon jetty construction, the downdrift beach first accreted due to landward ebb-delta shoal migration; however, once this sediment moved landward, it was slowly eroded and reworked northward. With the jetties in place, no new sediment was available to adjoining beaches, and they have faced continual erosion since approximately 1900.
A 1992 Section 111 study by the Corps presented several alternatives to deal with the erosion problems along the southernmost 2,500-foot stretch of Camp Ellis and Ferry Beaches. Original alternatives included 6 Plans:
Subsequent cost-to-benefit analyses by the Corps determined that none of the options were economically justified at the time (USACE, 1992).
In 1995, the Corps' Waterways Experiment Station (WES) laboratory completed a model study of the Camp Ellis Beach erosion problems. WES analyzed existing conditions in addition to some of the alternatives (and several variations) presented by the 1992 study. Conclusions indicated that any beach-fill plan would only be a temporary solution that would require periodic nourishment, and that an approximate 3,000 linear foot spur jetty was most effective in significantly reducing wave heights and beach erosion along Camp Ellis Beach.
In 2001, the Corps updated its 1992 Section 111 study at the request of the City of Saco and Congressman Thomas Allen. This study reviewed the original plans proposed in the 1992 study and found that Plan C, which included roughening approximately 1,000 linear ft of the shoreward most portion of the jetty and placement of approximately 275,000 cubic yards of beach-fill, was economically justifiable (USACE, 2001).
To date, the Saco Bay Implementation Team has been meeting to determine the most physically effective alternatives to alleviate the high erosion rates seen at Camp Ellis, while attempting to minimize impacts to the rest of the Saco Bay littoral system. At the time of the publication of this document, the Corps is in the process of collecting real-time wave and current data for the purposes of groundtruthing a nearshore numerical wave model. This model will be utilized to analyze several different structural alterations to the northern federal jetty, including several spur jetty configurations, roughening the innermost 1,000 feet of the existing jetty, removing the seaward end of the jetty, and several T-groin configurations along the shoreline. Results of the numerical model may indicate the most effective alternative for reducing storm wave heights, and subsequent erosion, along Camp Ellis beaches.
A successful overall long-term mitigation solution must not only take actions to substantially decrease existing erosion rates along Camp Ellis Beach (which range from 1-3 ft/year based on the data utilized in this report), but must also take into account the regular addition of sediment to the currently starved system. However, without a successful decrease in the existing erosion rate, any addition of beach nourishment material will only be a short-term, temporary solution. In order to help deal with this issue, it is recommended that the community of Camp Ellis address long-term coastal hazard issues through the development of a hazard mitigation plan, which would improve the community's resistance to flooding and coastal damage from storm events.
Last updated on January 10, 2006.
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