The Physical Aspects of the Mpenjati Estuary System

3095 Words May 6th, 2013 13 Pages
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
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The main aim of this study conducted on the Mpenjati estuary was to determine the effects of the beach processes on temporarily open/closed estuaries, in particular wave action as well as the transportation of sediment and to understand the influence that they may have on the state of the estuary mouth. The objective of the study was to determine the elevation of the beach profile or slope and grain size by using the Emery Board method as well as to analyze the natural stream flow into the estuary using flow duration analysis with relation to mouth dynamics.

Materials and methods.
The Mpenjati estuary is a temporarily open/closed estuary which is located approximately 165km Southwest of Durban. The river mouth is generally closed during the winter months and is enclosed by a sand bar separating the saline rich ocean water from the fresh water river.
On field, the time as well as tide was noted down. The equipment needed was two measuring poles/sticks with measurements in centimetres written on and a two meter length of rope. The Emery board method was used and all procedures were followed accordingly. Each group consisted of 20 members and was then subdivided again into groups of ten. Students took a turn to be a seaward surveyor and a landward surveyor, a data researcher and a geotechnical engineer. The respective measurements were taken starting from the baseline as well as the cross-shore data points.