Estuary Phy

Topics: Estuary, Coast, Geodesy Pages: 6 (1947 words) Published: September 13, 2011
The study was carried out o the 6th of August at the Mpenjati estuary and was done using different data collecting methods and analysis methods. The purpose of study was to determine the profile of the Mpenjati estuary and the flow of the estuary, these are shown by graphs that are found in the results section. Introduction

An estuary is a partially enclosed body of water along the coast line where freshwater from rivers meet and mix with ocean. Estuaries are transition areas from land to sea, and freshwater 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 ( Estuaries are divided into four different types depending on how they are formed. The four types are the coastal plain estuaries that is formed by rising sea levels that fill a already existing river valley, tectonic estuaries that is formed by folding or faulting of the land, bar built estuaries are formed when a shallow lagoon or bay is protected or covered by a sand bar or barrier land and fjords that are formed in a u shaped valley formed by glacial action (Garrison, 1995, Essentials of Oceanography). “The term “beach profile” refers to a cross-sectional trace of the beach perpendicular to the high-tide shoreline and extends from the backshore cliff or dune to the inner continental shelf or a location where waves and currents do not transport sediment to and from the beach”( Michael J. Chrzastowski Encyclopedia of Earth Sciences Series, 2005). The beach profile shape is constantly changing due to the affects of wave action and the storms that occur on the coast line, these waves or storms or a combination remove or deposit sands to the profile (Michael J. Chrzastowski Encyclopedia of Earth Sciences Series, 2005), another cause to beach profile change is human activity, we remove or add sand to create a more flat beach for recreational needs. The study was done at the Mpenjati estuary on Saturday the 6th of August 2011 and was carried out at 10:00am – 10:30am, the tide at this time was changing to low tide with a wave height of around 1.11m.The objective of the experiment done at the Mpenjati estuary was to determine the elevation of the beach profile or slope and to analyze the natural stream flow into the estuary using flow duration analysis in relation to mouth dynamics.

Materials & Methods
On the field the equipment needed is two measuring poles/sticks with measurements in centimetres and a two meter length of rope. The first thing that is needed is for the time and the tide to be recorded. Thereafter mark a parallel line from the back beach to the swash zone to fellow, appoint two people from the group to hold the measuring poles/sticks steady, move them around and keep the rope up between the poles/sticks, appoint one of the remaining people has the surveyor to check if the rope is horizontal between the measuring poles/sticks and the final person is to be used has a recorded to take down the readings. Starting from the back beach move the two measuring poles/sticks to determine the beach elevation, this is done by moving the rope in between the measuring poles/sticks with one stick (the one facing the land) having a fixed measurement (eg 160cm) and then adjust the rope so it is horizontal and the record the measurement on the seaward pole/stick, do this till you reach the swash zone. The next thing to do on the field is to calculate the estuary flow this is done by using the measuring poles/sticks, a watch and an object that is visible and is able to float, first determine the estuary depth and length by using the measuring poles/sticks and then determine the flow by placing two measuring poles/sticks over the estuary (left on the ground) over a recorded distance and release the object at the first measuring pole/stick and record the time it takes to pass the second pole/stick and then divide...

References: Garrison, 1995, Essentials of Oceanography: Wadsworth Publishing Company.
Michael J. Chrzastowski Encyclopedia of Earth Sciences Series, 2005, Encyclopedia of Coastal Science, 2, Pages 145-147
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