III. Shoreline Features and Process

Connecticut’s shoreline has a number of distinct land features such as tidal marshes, intertidal flats, bays, islands, headlands and bluffs, and beaches. These features are a direct result of a number of physical and geologic factors, including glaciation, changing sea level, waves, tidal currents and wind. Through the processes of erosion, transportation and deposition, these factors created and continue to modify existing landforms.

A. Processes

Erosion is the wearing away of the earth’s surface by the action of natural forces, such as wind and water. Sediments that are eroded from the shoreline are transported by wind, wave energy and tidal currents, and are eventually deposited elsewhere. Tidal marshes and mud flats are examples of areas resulting from depositional activity.
It is important to bear in mind that any feature under the influence of a number of separate but interrelated factors is dynamic. It must respond to both short and long term trends. Due to the influence of the tides, the ones where wave action affects the shoreline change daily. Changes in sea level, on the other hand, must be viewed as long term trends, causing modification of shoreline configuration over a period of thousands of years.  Because of their dynamic nature, no shoreline or shore feature should be considered as strictly erosional, depositional or stable, but rather, each should be viewed as continuously changing.

  1. Rising Sea Level
Approximately 8,000 years ago rising sea level first began to influence Long Island Sound, which was previously a freshwater lake.   Since that time, sea level has continued to rise and has “drowned” features which were previously upland, such as river valleys and glacial moraines. Such landforms as a small embayment (New Haven Harbor) and offshore islands (Norwalk Islands) subsequently appeared. In addition, tides and related currents began to affect the Sound. As climate change accelerates sea level rise, its role in changing coastal landforms grows.

  2. Wave Dynamics
Surface waves are produced by wind blowing over open water. Generally speaking, wave conditions are governed by three factors: fetch, or the length of unobstructed water over which the wind blows; duration, or the length of time for which the wind blows at a given speed from a given direction; and the velocity of the wind. As each of these factors is increased, larger waves can be generated. In the Long Island Sound area wind direction varies on a seasonal basis, with winds blowing generally from the south and southwest during spring and summer months, and from the north and northwest during the fall and winter. Winds blowing from southerly directions generate the waves which most dominate Connecticut’s shoreline.
As waves traveling across Long Island Sound enter water of increasingly shallow depth, they become gradually steeper until their crests fall forward as breakers, creating what is commonly known as surf: Since the Sound is almost entirely sheltered by Long Island and Fishers Island, fetch is limited and large waves, such as those which break on shores exposed to the open ocean, do not reach Connecticut’s coast. Normally, waves breaking on the Connecticut side of Long Island Sound range in height up to six feet, although during infrequent storms and hurricanes larger waves can be expected.
As waves approach the shore and break, they release energy. This energy erodes and transports shoreline sediments in three ways. Longshore currents, which are created when waves break at an angle to the shore, carry sediments parallel to the shore. Also, waves may transport sediments either on or offshore, depending upon the nature of the actual “breaker.” The steeper “plunging” breakers tend to move material offshore, while the less steep “spilling” breakers tend to move material onshore.  The zones in which waves exert the most influence (where breaking occurs) are changed daily due to rising and falling tides

  3. Tidal Currents
Currents created by the action of the tides are also important in the erosion, transportation, and deposition of sediments along our shores, particularly at inlets, bays and river mouths. When tides enter small coves, harbors, and other embayments with inlets (constricted openings), the velocity of the current is significantly higher. The narrower the inlet, the higher the current velocity. At inlets, an equilibrium situation normally exists; that is, there is a balance between the size of the inlet and the volume of the tidal exchange. If an inlet is below a certain equilibrium size (due to the deposition of sediment from storms, etc.), stronger currents will erode the material from the inlet, eventually returning it to equilibrium. If, on the other hand, the size of the inlet is above the equilibrium, currents are slower and may deposit material at the inlet.
In bays and other semi-enclosed quiescent bodies of water along the shore, finer materials carried in by tidal currents are deposited, giving rise to intertidal mud flats. At river mouths and, in some instances, at points of land which project seaward, tidal currents can act in conjunction with longshore currents to move material along the shore and modify magnitudes and directions of longshore currents.

  4. Winds
Winds, in addition to generating waves, are also capable of moving sediments along the shore above water level. Their influence is most apparent in the formation of sand dunes. As mentioned previously, normal wind direction varies seasonally. Hurricane force winds are most likely to occur during the late summer and fall. Waves generated by hurricane winds cause significant and sudden changes to our shores, such as breaching barrier beaches or filling inlets.

  5. Biological Processes
Biological factors are important in the formation of shoreline features, particularly tidal marshes and dunes. Beach grass and other dune vegetation as well as various salt marsh species encourage the deposition of sediments by acting as physical barriers to the transport of materials, and by stabilizing materials with their root systems. 

B. Features

  1. Headlands and Bluffs
In Connecticut, headlands may be composed of glacial drift and/or bedrock. Their original formation is a direct result of glacial scouring and deposition. Where these features are composed of glacial drift, which is easily eroded, they provide a major source for sediments which are then transported to other sites, forming beaches, marshes and mud flats. In contrast to drift, bedrock is highly resistant to erosion, and as a result, is only weathered slowly by waves, winds and tidal currents. Headlands are easily recognized as higher hilly forms projecting seaward. Bluff Point is a typical headland which provides a sediment source for Bushy Point Beach.

  2. Beaches
Beaches are generally considered to be erosion prone. However, their initial development is a result of the depositional process. The character of the beach is regulated by the balance between erosional and depositional forces. When these forces are in dynamic equilibrium, beach form remains constant. When the equilibrium is altered, the beach may either grow or diminish in size. For example, if the sediment source of the beach is depleted, either as a result of a natural process or through the construction of a man-made feature such as a sea wall, the beach will recede. If, however, additional sediment becomes available and is transported to the beach, it may increase in size.  Another factor affecting beaches is rising sea level. As sea level rises, the beach as a system may retreat in response to changing balance between erosion and deposition. Thus, it may eventually override the land behind it. Such a situation exists at Cedar Island, Clinton, where peat deposits project from the beach face.

Several types of beach are found on the shores of Long Island Sound. Included are:

• Spits, or projections of sand attached at one end to an island or the mainland

• Tombolos, or stretches of sand connecting an island and the mainland or two islands

• Pocket beaches, which occur in small crescent-shaped coves and directly front uplands.

Spits and tombolos may be referred to as barrier beaches in instances where they extend parallel to the mainland but are separated from it by a body of water or marsh. Examples of these types of beaches may be seen at Griswold Point in Old Lyme (spit), and on the Norwalk Islands (tombolo).

Beaches show characteristic profiles which are related to waves, wind, tides and biological activity.  Beaches change constantly in response to variations in tidal ranges, weather and surf conditions. Dunes formed by aeolian (windblown) sand deposits vary in response to wind and sand supply. Vegetation (such as Beach Grass) growing on the dunes stabilizes them and encourages their growth. Dunes provide an important reservoir of sand which may replenish beaches during times of severe erosion.  Typical beaches in Connecticut are relatively narrow with steep faces composed of coarser sand and some gravel. They generally lack well developed dunes.