The Maintenance of Beaches

The Maintenance of Beaches (1975)
by A. J. Bowen, D. P. Edmond, D. J. W. Piper and D. A. Welsh
Technical Report
Institute of Environmental Studies
Dalhousie University, Halifax; 582 p.

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(9) Crescent Beach (Green Bay Beach), Lunenburg Co.
a) Physical and geological setting: Crescent Beach is a barrier system in the form of a tombolo extending 2km across Green Bay from the mainland to George Island, one of the LaHave Islands (Fig. 3.26). The barrier, carrying the main road to George Island and Bush Island, is now very little wider than the road (Fig. 3.25). The system is now almost completely artificial, the boulder seawall forming the backshore along most of the beach. This beach is a major recreational area used by more than 500 people/day in summer13. Vehicles have direct access to the beach (in order to impose a speed limit, the Motor Vehicle Act was amended to include beaches as public highways). Before the highway was paved, the local residents used the beach rather than the unsurfaced road in their journeys to and from the islands. 

The bedrock in the area is of Meguma sandstones and slates which have been eroded down to a level close to the present sea level. Till is not common in this area and there is no appreciable erosion of the bedrock; the few shale pebbles, found

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near outcrops of the Meguma, do not provide a significant I sedimentary input. The Petite Riviere, which enters Green Bay 2 km southwest of Crescent Beach, does not appear to be a significant source. 

Offshore, between the shoals at the entrance to Green I Bay and the beach, there is an extensive sheet of fine sand. The I beach itself is of very gentle gradient and is composed of very fine sand with a few shale pebbles (Fig. J.24) .The beach sand is petrologically mature; old sand in which the resistant grains I have survived preferentially. This sand has been moving landward with the rising sea level for a very long time. The relative I absence of the weaker fragments confirms the lack of a significant local supply of sand from rivers or cliffs. The only source for I the beach is the sand in Green Bay which has, in a sense, already I been left behind, some at depths of more than 10 m. Since there is very little sand coming in to this system, it has always been I very vulnerable to disturbance. It is hard to envision in looking at the present day photographs that within the life time I of many of the local residents, the beach contained a major dune system backed by a very extensive salt marsh.

 b) Dunes and vegetation: The remnants of the dune system, now only damaged fragments seawards of the road, are disappearing rapidly. The presence of artificial barriers has encouraged the I loss of sand to the backshore by both wind and storm overwash, and only the extreme ends of the system have recognizable dunes.

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All the remaining dunes have an eroded, unvegetated foot Ion their seaward face, with very few colonizing plants. The I boulder wall catches very little sand and there are only occasional clumps of dune grass, rose and introduced weeds between I this wall and the road. Most of the beach sand therefore blows I straight through the system into the lagoon. The dunes at the ends are eroding and trying to retreat; the presence of the I road prevents this, and they are therefore slowly being blown away. 

The sand flats on the northern side of the road are I increasing in size and height as the sand blows through from the I beach. The high rate of accumulation inhibits plant growth and the area is poorly vegetated. Some of the high spots are now I being colonized by dune plants. At both the eastern and western ends, the remaining dunes reduce the sediment movement across the I barrier and the salt marsh community has survived. The difference along the backshore illustrates very clearly the advantages of dune systems over any artificial structure for keeping the sand on the beach. 

c) Human impact: Crescent Beach has a long history of use. I The earliest deeds on the property, which was privately owned I until 1951 when it was given to the province, stated that the beach must be available to the public for "pleasure, bathing and I the gathering of sea manure". Apparently the beach has been a popular recreational area since this region was first settled. I At the turn of the century the dune line was intact

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along the whole length of the beach, although the outer slope was described as "cliff-like" in places indicating that the system was eroding. There was a very extensive salt marsh behind the i' dune; cutting rights for the salt hay were sold at public auction each year. However, in the great winter storm of 25-27 January 1905, the sea broke right through the system. The breach was repaired by local residents who dumped whole spruce trees in the gap. It is interesting that the local people, without government advice, did exactly the right thing and did it quickly (Speed is important because the beach sand is continually lost to the lagoon until the breach is closed). The dunes recovered and by 1920 a continuous dune line had been reestablished. However, in the mid 1920's during an exceptionally dry summer, the dune grass caught fire and both the dunes and marsh areas were severely burned. The fire damaged the roots of many of the plants, the dune vegetation became sparse, sand was blown inland and the salt marsh, severely damaged by the fire and then subject to the accumulation of the wind blown sand, never recovered. Erosion became an increasing problem; storms frequently washed through the dunes and cut the road. In 1938, long plank seawalls were built along most of the beach. At the eastern end part of the wall failed in the early 1940's and a line of old car bodies was placed in the gap. These trapped sand effectively and a steep, narrow dune system developed around them. From time to time, various attempts were made to repair the plank seawall, but the system continued to

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erode and the central section of the beach was severely damaged in a storm on December 30, 1956. consequently, early in 1957, a seawall of large boulders or 'armour rock' (Fig. 3.25) was built by Public Works Canada and the road graded and surfaced. The remaining dunes continued to erode, the storms of February 1972 damaged the west end which was patched up with old posts and driftwood. 

The use of the beach as a highway to the islands and as a racing track for sport driving created conflict with the ordinary recreational use. Part of this problem was resolved when the Motor Vehicle Act was extended to beaches and there is now 15 mph speed limit on the beach. In July 1970, a more drastic solution had been tried; boulder barriers were placed to block vehicle access to the beach. After great local outcry and considerable conflict, the boulders were removed and the beach is still used as a road and parking lot. As the traffic on the beach face causes very little physical damage to the system, the conflict was about compatibility of two uses of the beach, by people and by vehicles, neither of which has any significant influence on the stability of the system. However, the problem is relevant because it illustrates the difficulties that provincial authorities face in keeping vehicles out of specific areas, particularly if the areas have a tradition of vehicle use.

Sand removal has always been strictly prohibited and

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there has never been any significant removal. The removal of the sea weed washed up on the foreshore, the sea manure, naturally includes a limited removal of sand. Although irrelevant now in view of the general condition of the beach system, this removal has nourished local gardens at the expense of the beach for many years. The band of flotsam along the foot of the dunes, containing the seeds of the primary colonizers and the nourishment to support their growth, is a significant factor in the stability of the system. 

d) Evolution and development: The beach sand at Crescent Beach is old. The present situation, where there is no source for new sand for the beach, is typical of the conditions during the last few thousand years. As the beach retreated landwards up Green Bay, this sand moved with it, being rearranged to maintain the beach profile relative to the rising sea level. In the natural state the beach must continue to retreat to survive, either in the form of a steady transgression or as a sequence of failures, recovery and dune development and, again, failure. 

Man's impact has accelerated the natural tendency of the beach to fail. Minor disturbances, the removal of sea manure, the harvesting of the dune grass and the maintenance of a track to the LaHave Islands all probably contributed but the severe deterioration seems to have been associated with the fire in the 1920's.

The various subsequent efforts to stabilize the beach

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were doomed to failure. Since there is no sand supply, the beach must retreat landwards to recover, reworking all the sand now deposited in the flats behind the road. The latest attempt to protect the road, the boulder wall, represents the opposition ) the natural processes rather than adaptation to them. The commitment to maintain such a barrier will be a continuing financial burden, a cost which is hidden in the accounts of departments with large budgets. The pressure, once the capital cost is committed, to repair rather than abandon such a system is obvious; if it is abandoned the capital must be found for an alternative route. However, it is clear that as long as sea level is rising at the present rate, the barrier will have to be continually improved if it is to survive. In practice, critical problems will arise on a much more rapid time scale than that associated with the 4 mm/yr rise in sea level.

The immediate future will see the disappearance of the dunes at both ends of the system and the consequent need to protect the road and the backshore then exposed. This will require a further commitment; if the road is to survive the armour rock will have to be extended along the whole beach. 

At the same time sand will continue to blow over the road into the lagoon, reducing the sand supply on the beach face and, eventually, the ability of the beach to absorb the increasing wave energy;  Storm damage to the barrier and road will then become increasingly common.