Variation of Beach Morphology along the Saco Bay Littoral Cell

Historical Background

Jetty Construction

In the 1800s, the Saco River served as an integral harbor and port-of-entry for the textile mills of Saco and Biddeford. Due to navigational hazards caused by shoaling at the mouth of the river, the Corps initially placed wooden bulkheads and several buoys to mark shoaled channel areas in 1827. In 1865, Congress authorized the construction of a rock jetty at the northern end of the Saco River. Since initial construction in 1869, a southern jetty was added in 1890, and numerous improvements and repairs have been made to keep the jetties structurally sound and attempt to control river shoaling (Table 1).

Dredging and Beach Nourishment

Maintaining a safe, navigable channel at the Saco River has been a focus of the Corps since beginning the navigation project in 1827. Periodic dredging of the channel has been necessary to keep the navigation channel open. Although the actual volumes vary from report to report, Table 2 summarizes some of the dredging activity at the Saco River from 1827-1992. Most of the dredged sediment was used for beach nourishment at Camp Ellis. On average (from 1928-1992), the Corps dredged approximately 11,100 yd³/yr from the navigation channel at the Saco River. From 1969-1996, the Corps has placed an average of 16,920 yd³ of sand at Camp Ellis Beach as some form of beach nourishment. The Corps has also dredged extensively to maintain a navigable inlet at the Scarborough River at the northern end of Saco Bay (Table 3), however the majority of dredged material was discarded through offshore disposal. 1996 dredging of the Scarborough River resulted in the placement of approximately 90,000 yd³ of sediment in a nearshore berm off of Camp Ellis Beach (Irish and Lillicrop, 1999). On average, the Corps dredged approximately 16,140 yd³/yr for the Scarborough River navigation project.

Previous Studies

Several studies, theses, dissertations, and reports have focused on coastal processes and sediment movement patterns within Saco Bay. In addition, the Corps conducted many studies, dating back to 1882, in conjunction with the federal project at the Saco River (Table 4).

Farrell (1972) noted a distinct fining in sediment size from south to north, in addition to accretion occurring at Pine Point, at the northern end of Saco Bay, and postulated a northerly dominant direction of sediment transport. Work by Wommack (1979) in support of a report prepared for the City of Saco also suggested a northerly-directed net transport direction. In addition, Nelson (1979) found significant evidence of a net northern transport based on analysis of historic shoreline changes. Recent work by Kelley and others (1995) and Barber (1995) created a sand budget for Saco Bay based on previous work by others, and coupled the use of side-scan sonar imaging, bottom sampling, and historical maps and aerial photographs to further conclude that not only is the dominant net transport in a northern direction, but that the Saco River has been and still is the major sediment source for Saco Bay.

The most complete Corps' study, completed in 1955, indicated that Camp Ellis underwent accretion immediately following construction of the northern jetty, from about 1872-1909. This accretion probably occurred due to the onshore migration of abandoned ebb-tidal delta shoals by wave action, consistent with similar phenomena seen at inlets following stabilization (Hansen and Knowles, 1988). However, since about 1909, Camp Ellis has undergone severe erosion. From 1859 to 1955, the Camp Ellis shoreline lost 61,933 m³/yr of sand (USACE, 1955). This erosive trend has continued to the present on the order of 2-3 ft per year, resulting in the loss of 33 homes since 1968 (Saco Bay Planning Committee, 2000). For comparison, the majority of sandy beaches along Maine's coastline have an average annual erosion rate of generally 1 foot or less (Nelson, 1979). The high erosion rate at Camp Ellis may be attributed to several factors:

interruption of natural sediment supply to the downdrift beach and scouring adjacent to the jetty due to the northerly-directed alongshore current;
diversion of riverine sediment farther offshore into a deep-water ebb-tidal delta; and
wave focusing along Camp Ellis beaches due to reflection of waves by the jetty.

Throughout the history of the navigation project, the Corps maintained that

sediment transport was in a southern direction;
the main sediment source was reworked offshore material; and
there was no evidence that the federal project was responsible for erosion problems seen at Camp Ellis (USACE, 1955, 1976, 1991).

In 1991, the Maine Department of Environmental Protection and City of Saco requested a study by the Corps under Section 111 of the River and Harbor Act of 1968 (PL 90-483), suggesting that the northern jetty of the Saco River navigation project was responsible for erosion problems in the area. The Corps conducted a Section 111 Study in 1992 in order to determine if shoreline damages in the vicinity of Camp Ellis were attributable to the federal navigation project. An alternatives analysis including five different potential solutions to the erosion problem was considered. Conclusions found that the existing structure appeared to be causing reflective forces that may be contributing to some extent to the erosion occurring in the area. However, it was also noted "significant erosion would likely occur even in the absence of the navigation project" (USACE, 1992). Because the potential benefits of several alternative solutions did not offset estimated costs of those solutions, no further federal involvement was deemed necessary at the time.

It was not until after a 1995 model study (Table 4) by the Corps' Waterways Experiment Station (WES) that the Corps acknowledged that the dominant sediment transport direction is from south to north, and that the jetty structure caused an increase in wave sizes due to the reflectivity of the jetty, which subsequently caused increased erosion along Camp Ellis (USACE, 1995a). This study was based on the construction of a 1:100 scale physical model at the Corps' WES laboratory in Vicksburg, Mississippi. The model study included the modeling of several mitigation alternatives, including structural improvements and beach-fill.

Regional Planning

While Camp Ellis and parts of Ferry Beach and Hills Beach are experiencing accelerated erosion, Old Orchard Beach and Pine Point at the northern end of the bay are experiencing accretion (e.g., Pine Point grew 137 m seaward from 1877 to 1923 (Farrell, 1972)). Therefore, beach management issues along Saco Bay need to be dealt with on a regional basis.

The Southern Maine Beach Stakeholder Group, in connection with the Maine State Planning Office, published a document titled Improving Maine's Beaches in April 1998 (MSPO, 1998). The Group, comprised of local property owners, municipal officials, business, environmental, and state organizations from within Saco Bay and beyond, outlined issues of concern and made recommendations on how to address them.

In 1999, the Saco Bay Planning Committee was formed as a result of the Improving Maine's Beaches document. This Committee released the Saco Bay Regional Beach Management Plan (SBPC, 2000), which focused on identifying and addressing beach management issues in Saco Bay at local, state, and federal levels. Emphasis was placed on the federal jetty at Camp Ellis as having a "...profound effect on the sand flow for all of Saco Bay, depriving the southern end... of sand and creating an abundance at the northern end." Such regional planning is vital for the long-term solution of the localized erosion problem at Camp Ellis.

The Saco Bay Implementation Team, comprised of property owners, municipal officials, and state and federal organizations (including the Corps), has been meeting for several years now in hopes of developing a solution to the erosion problems at Camp Ellis Beach. In 2001, Congress appropriated $350,000 to the Corps for a design/feasibility study, followed by $1.2 M funding in 2002 for jetty alterations.

Contents Introduction Historical Background Methods Results Discussion Recommendations Conclusions Additional Study and Research References Appendix A

Last updated on January 9, 2006.