The Physical Aspects of the Mpenjati Estuary System
A study on the physical aspects of the Mpenjati estuary- beach system.
Roxanne Munsamy
University Of KwaZulu-Natal
Abstract
A study was conducted at the Mpenjati estuary on the 4th of August 2012 to determine the physical aspects within the estuary beach system. This paper gives an overview of the factors affecting the slope of the estuary, sediment sizes and the tidal prisms. The beach slope was measured using the Emery board method and it was found to be characteristic of the KwaZulu-Natal coastline. Wave energy and sediment transport rates along the beach morphology are interlinked, high energy storms tend to erode and flatten beaches whilst lower energy waves tend to be responsible for the reverse process- rebuilding breaches. A flow duration curve was produced and it was established that the Mpenjati estuary mouth is opened with the flow duration of 0.26 m3/s. Sewage works found to play a greater influence on flow rate as opposed to abstractions for irrigation. The estuary was open for sixty five percent of the time between the periods 2000 to 2006.
Introduction
A general understanding of an estuary is a region through which a river discharges into a sea and in a Southern African context the following is a widely accepted and concise definition of an estuary “It is a partially enclosed coastal body of water in which is either permanently or periodically open to the sea and within which there is a reasonable variation of salinity due to the mixture of sea water and fresh water derived from land drainage” (Day, 1980). Hence estuaries are the transition zones from land to sea, and fresh water to salt water. Although estuaries are influenced by the tides, they are protected from the full force of ocean waves, wind, and storms by landforms such as barrier islands (water.epa.gov). Interactions between salt water and freshwater forms the basis of estuary hydrodynamics, together with the movement of sediment, the effects of wind, waves, anthropogenic inputs and
Roxanne Munsamy
University Of KwaZulu-Natal
Abstract
A study was conducted at the Mpenjati estuary on the 4th of August 2012 to determine the physical aspects within the estuary beach system. This paper gives an overview of the factors affecting the slope of the estuary, sediment sizes and the tidal prisms. The beach slope was measured using the Emery board method and it was found to be characteristic of the KwaZulu-Natal coastline. Wave energy and sediment transport rates along the beach morphology are interlinked, high energy storms tend to erode and flatten beaches whilst lower energy waves tend to be responsible for the reverse process- rebuilding breaches. A flow duration curve was produced and it was established that the Mpenjati estuary mouth is opened with the flow duration of 0.26 m3/s. Sewage works found to play a greater influence on flow rate as opposed to abstractions for irrigation. The estuary was open for sixty five percent of the time between the periods 2000 to 2006.
Introduction
A general understanding of an estuary is a region through which a river discharges into a sea and in a Southern African context the following is a widely accepted and concise definition of an estuary “It is a partially enclosed coastal body of water in which is either permanently or periodically open to the sea and within which there is a reasonable variation of salinity due to the mixture of sea water and fresh water derived from land drainage” (Day, 1980). Hence estuaries are the transition zones from land to sea, and fresh water to salt water. Although estuaries are influenced by the tides, they are protected from the full force of ocean waves, wind, and storms by landforms such as barrier islands (water.epa.gov). Interactions between salt water and freshwater forms the basis of estuary hydrodynamics, together with the movement of sediment, the effects of wind, waves, anthropogenic inputs and