Throughout the known history of the Higgins Beach barrier spit system, the shoreline has receded in a landward direction and the spit has extended to the northeast to restrict the inlet of the Spurwink River against the Cape Elizabeth foreland.
This demonstrated history parallels a generalized geologic history of Maine barrier spits generally recognized by geologists who have studied these beaches (Hussey, 1970; Nelson and Fink, 1978; Nelson, 1979; Schnitker, 1974; Timson, 1979; Timson and Kale, 1977).
Maine barrier spits have migrated landward and extended their free spit ends over, at least, the past 3,000 years during a period of slow sea-level rise.
The Holocene Transgression is that period of sea-level rise which followed glacial periods. Throughout the transgression, the eastern seaboard was progressively drowned by a rising sea level, which was caused by the addition of glacial ice meltwater to the world's oceans and constant subsidence of the continental margin.
During this sea-level rise, beaches were created and forced by natural processes to migrate landward. In Maine, the landward migration of barrier spits is further complicated by an irregular shoreline and a paucity of glacial sediments to be reworked into beach sediments.
At one time during its history, Higgins Beach probably was part of a larger beach system which included Scarborough Beach and extended from Prouts Neck to the Spurwink River. During this phase of its history, the large beach system was afforded a large supply of sand available as a beach and dune substrate. This supply, once part of the beach system, could move from one end of the beach system to the other through seasonal changes of bi-directional littoral currents.
If one assumes that the recessional rates observed on the beach today will continue for 25 to 50 years in the future, then it is a simple task to define the shoreline position which would result from erosional processes.
Defining future shoreline positions at Higgins Beach is more difficult than the previous task states because of the historical fluctuation of shoreline recession rates and the stabilized nature of about 70% of the beach's length.
Two scenarios are offered: one where shoreline recession takes place into the future assuming no shoreline development; and, a second which assumes future shoreline recession with existing development remaining.
Over the next 25 to 50 years, we should expect that the presently developed section of the beach will be smaller in area than it is today. This judgment is based on the knowledge that one large structure and a fronting seawall were removed as a result of the 1978 storms, and the tenuous nature of several existing dwelling structures. This will be further elaborated on in Section 3.6. Just how many seawalls and structures and their locations will not be replaced after future damage cannot be determined.
Figure 9 illustrates future shoreline positions assuming the exclusion of past development. Future shoreline positions are presented for a minimum recessional rate, exhibited in the past to be about .36 m/yr (1.2 ft/yr), in 25 and 50 years, and a maximum average rate of 1.6 m/yr (5.8 ft/yr) exhibited in the past in 25 and 50 years.
If we removed the frontal row of cottages, the present shoreline would almost immediately adjust to the change by migrating back about 20 meters. In 50 years, assuming the minimum recessional rate expected, the shore would migrate landward another 20 meters, accompanied by an extension of the spit into the Spurwink River. The natural shoreline at that time would be just behind Kent Street.
In 50 years, assuming the maximum average recessional rate of 1.6 m/yr, the shoreline will migrate back to the very landward edge of Bayview street, a total landward shift of about 80 meters from its present position. After such a period, the Spurwink River inlet probably would have migrated further to the west than its present position, and the rear of the barrier spit would be attached to the granite-based island now behind the marsh.
Figure 10 illustrates a 25- and 50- year scenario assuming existing development remains and that the present rate of recession continues for those time frames.
The end result of this scenario would be the creation of a beach cul-de-sac at the ends of Pearl and Ashton Streets, and a recession to the Kent Street Extension on the spit end, accompanied by a westward shift of the present inlet.
Future shoreline positions, however, do not indicate the changes which will occur on the intertidal beach. Observations of beach profiles on the beach today indicate that, if shoreline recession continues into the future, the upper beach surface will lower. The lowering of the beach surface will take place by the normal transfer of beach sand from the west to the east during periods of prevailing winds and by a transfer of sand offshore during northeast storms.
Presently, for many days of the year, the high tide line exists at the base or up on the lower portions of those seawalls which protrude the farthest toward the ocean seaward of Kent Street. In 25 years, it will be safe to assume that these walls will be the waters edge for much of the tidal cycle in all but the summer months when normal beach accretion occurs seasonally.
The upper beach surfaces remaining exposed at high tide at the end of Pearl and Ashton Streets will be reduced in area in 25 years. The only sizeable area of high tide beach remaining along the entire length of the beach will be at the spit end.
The February 7-8, 1978 northeast storm produced significant damage at Higgins Beach. An old hotel and seawall were damaged beyond replacement and many shorefront cottages and seawalls sustained damage from storm wave forces and wave surges rushing over seawalls.
Flooding due to storm tides was also a severe problem along the low-lying portions of the rear of Higgins Beach. Damage resulted from short-circuiting of domestic electrical systems, as well as water, and floating debris.
Wave surges which overtopped frontal seawalls travelled rapidly back to second and third row cottages since adequate drainage of storm surge did not exist in a seaward direction.
The dollar loss due to coastal storm damage during the 1978 storm is presented in Section 4.11. Coastal storm damage resulted from:
Based upon observations of still evident storm damage, answers to storm damage questions in the property owners survey of the study, and expected storm frequencies in the next 25 year period, a storm flood hazard map is presented for the Higgins Beach area (Figure 11).
The flood hazard map augments the flood hazard boundary map of H.U.D. by discriminating between flooding and wave damage. The flood zones delineated are:
1,700 feet of shorefront along Higgins Beach is stabilized by seawall structures. These seawalls vary as to their structural integrity to withstand storm wave forces and in their environmental impact on the intertidal beach. The seawall types and their characteristics on Higgins Beach, from west to east, are:
The structural stability of these walls during future northeast storms is reflected in the determination of the flood hazard zones presented in Figure 11.
A healthy coastal barrier beach in Maine consists of a fairly wide dune field, a foredune ridge which extends above mean high water by 5 or 6 meters (15 to 18 feet), an 8 to 17 meter-wide (25 to 50 foot) beach berm and a beach face. Such a beach provides recreational surfaces at low and high tides and a protective foredune ridge which is flexible to storm wave erosion. Several Maine beaches exhibit this configuration because they have an adequate supply of sand and are capable of healing after large storms.
Higgins Beach, however, exhibits a different set of characteristics. The dunes that exist are low and partially devegetated; the beach berm fronting all but the spit end is very narrow or non-existent; and, the average beach surface is only 1 or 2 meters above the mean low water level of the ocean.
These characteristics result from several factors. First, the beach is mostly composed of fine to medium-fine sand. Sand of this size naturally forms a low beach of gentle seaward slope. Second, the beach is losing sand to the estuary and the offshore. The sand is not being replaced by an external source or by dune sand which would normally aid in the replenishment of reach sand after a storm. And third, development on the dune field of Higgins Beach has reduced the foredune height and "locked-up" dune sand behind seawalls. The resultant beach configuration is one which provides very little natural protection to structures built on the foredune and very little beach recreational surface at high tide.
This section documents that Higgins Beach will continue to lose sand in the future, further reducing the beach's natural capacity to provide a recreation surface and to protect the backdune area from storm waves and floods. The beach surface will continue to lower to a point where the base of the existing seawalls will be struck by waves for a greater time period of a tidal cycle.
Unless future steps are taken to alter the present course of events, future storm damage to shorefront property will be greater and even more frequent, perhaps to a point where a moderate northeast storm would incur more than minor damage. Also, the beach surface at high tide will be almost non-existent except at the undeveloped spit end. The recreational capacity of the beach will be far less than it is today. Humans will have assisted in the destruction of the very resource which attracted them to Higgins Beach originally.
The geologic analysis presented in the Management Plan was undertaken during the latter parts of May, June, and early July for presentation to the public in July of 1980 and as a base for determining the management options. The scope of the study, the limited funds, and the time-frame available for undertaking the analysis limited the data base mostly to existing information, aerial photograph and chart analysis, and geologic field observation. Three beach profiles were obtained for direct measurement.
These limited data pose confidence limitations on the transport model and geologic predictions from which the management options were selected, as the limited data had to be expended for posing certain geologic assumptions and interpretations based upon the consultant's accumulated knowledge and experience.
Although quantitative data are presented in the geologic section, much of these data are based upon initial assumptions. Specifically, posing assumptions are necessary in order to project future shoreline recession rates and to determine a transport budget model. While these final, numerical determinations may be in doubt, the trends which they represent are more viable. They are backed by geologic observation and experience as well as being in agreement with local resident observations. However, the science of coastal geology is limited in many respects to presenting conclusions as long-term, average trends: and these trends do not preclude shorter-term changes in trend nor the "catastrophic" event such as a hurricane.
Limitations of the geologic information on the beach system are one reason why the management options requiring large capital expenditures were not selected by the committee or the public for final recommendation. Rather, the final management recommendations stipulate flexible actions which can be implemented whether the beach becomes progradational or recession occurs at a more rapid rate than what is presented here.
This plan also calls for further monitoring of beach changes and prophecies for a local committee to add more detailed information to the existing data base such that future updating of the geologic knowledge of Higgins Beach can be accomplished at a reasonable cost.
References:
(1) Hussey, A.M., II, 1970. Observations on the origin and development of the Wells Beach Area, Maine. In Shorter Contributions to Maine Geology, Maine Geological Survey, Bull. 23, 58-68.
(2) Nelson, B., 1979. Shoreline changes and physiography of Maine's sandy coastal beaches: Unpub. MS Thesis, University of Maine at Orono, Dept. of Oceanography, 302 pp.
(3) Nelson, B., and Fink, L.K., 1978. Geological and botanical features of sand beach systems in Maine: Critical Areas Program, Maine State Planning Office, Augusta, Maine. 266 pp.
(4) Schnitker, D., 1974. Post-glacial emergence of the Gulf of Maine: Geol. Soc. Amer. Bull., 85: 491-494.
(5) Timson, B.S., 1979. A preliminary model for the genesis, evolution and maintenance of Maine barrier beaches. (abs.): Geol. Soc. Amer., NE Sect. Annual Meeting, Philadelphia, Pa.
(6) Timson, B.S., and Kale, D., 1977. Maine shoreline erosion inventory: open-file rpt., Maine Geological Survey. Augusta, Maine.
Creation Date: October 30, 1997
Reproduced with Permission of Barry Timson and Arthur Lerman