Beach Lagoon

Coastal lagoons are defined as “shallow coastal water body separated from the ocean by a barrier, connected at least intermittently to the ocean by one or more restricted inlets, and usually oriented shore parallel” (Kjerfve; 1994). Barnes (1980) describes the processes that occur for the creation of lagoons as low energy constructive waves, whose swash is more powerful than its backwash. As a result the waves break over a large distance but gently. The waves approach the beach at an angle as opposed to being parallel to it. This enables the material to be moved along the coastline, as the material is pushed backwards to the ocean. This process is commonly known as longshore drift. Longshore drift allows for the further development of sand

It is 3.7km long (north-south) and 1.8km wide (east-west) and is a natural percolating coastal lagoon. There is no natural channel that connects Lady’s Lake to the ocean. Due to this a man-made channel is often constructed during winter and spring months, after heavy rainfall when the water level in the lake increases, as the seepage through the barrier wouldn’t suffice. This prevents backing up in sewers and flooding of the local area and allows the farmers to use their land all year round. The man-made channel normally stays open for some weeks before being closed naturally due to lateral drift and thus isolating the lake again (Healy; 1997). This practice has been used since the seventeenth century (Murphy; 1956). The main source of water transfer in Lady’s Lake is through seepage through the barrier. Even though this lagoon is isolated from the ocean it is still subject to fluctuations in water level and salinity as a result of the dune barrier rupturing. Past sediment research indicates that a freshwater lake formed around 4500-5000 years ago, and existed as one till 1700 years ago when salt water entered it first (Healy; 1997). Due to ongoing coastal processes, lagoons, in a geological sense, are short living. This is mainly due to the barrier evolving due to lateral drift and succession. Lagoons are one of the most severely affected coastal habitats, due to changes in sea level, storm surges, which can damage the barrier, and modifications of the coastline which alter long-shore currents or the supply of