Topographic Beach Survey

A beach survey is a form of rapid data collection that measures the elevation and position of points and presents them as a plot which may include contours, elevations and 3D models.  This data can then be used for a variety of purposes such as the calculation of beach volumes and movement of beach material.  At the present time the surveys are generally carried out using Global Positioning Systems (GPS), providing high accuracy data to +or-3cm and the ability to easily revisit a site over time, allowing us to build up a picture of how the beach is changing. Data collected include the elevation, co-ordinates (eastings and northings) and the type of sediment for each point.

What is a beach profile?

This is a series of points recorded perpendicular to the sea along predetermined lines.

These lines can be repeated as often as we require to help us best understand the movement of material at that particular point along the beach front.  These profiles are used to build up a picture which allows us to better understand how the beach responds to storm events, the long-term volume changes across the beach and to identify areas that are at an increased flood and erosion risk.  If beach profiling is combined with Bathymetric Surveys (profiles on the seabed recorded from a boat) then we can assess the full zone of wave influence on the beach gaining a much wider understanding of the changes that are happening.

When do we carry out these surveys?

Beach profile surveys are usually carried out twice a year (around autumn and spring time) to reflect seasonal changes in wave energy.  The surveys are carried out during periods of low spring tides to ensure we get to a specified depth and that we capture the full active beach profile.

Where do we carry out these surveys?

The profiles are surveyed at an average interval of between 200m to 250m around the open coastline.  We carry out these surveys from Portsmouth Harbour through to Selsey Bill. Surveys are not normally conducted within the harbours due to their stable and sheltered nature.

Why do we carry out these surveys?

To investigate the effects of seasonal changes around the coast and to gain better understanding and knowledge of the coastline and its processes.  This helps to design better coastal defences to protect against both coastal flooding and erosion. The information is also used to help with current beach management so we can determine when we need to undertake work at a particular location. This is done by comparing previous datasets and interpreting the changes that have taken place.

What equipment do we use?

The equipment we generally use is Real Time Kinematic GPS .  This allows us to gather data accurately and efficiently with a vertical accuracy of +/- 30 mm and a plan accuracy of +/- 15 mm.  We use a base station and several mobile receivers or "rovers".  The base station transmits corrections via radio signals to the rovers allowing the surveyor to record their position to within +/-30mm at any point.  Data gathering this way allows for speed in data capture which is both accurate and useable. 

 

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