Beach & Marina Surveying
Coastal and marine surveying services. El-Eman Office provides beach and marina planning.
Vertical datums and tides in coastal work
Beach and marina surveying differs from land surveying because the sea level itself changes over time. A clear vertical reference must therefore be set for the project, such as the official datum for the area or a level tied to a tide gauge station, and marine measurements are corrected to it.
- Record the time of every depth measurement so it can be corrected for the water level at that moment.
- Install a permanent level benchmark near the site and tie all the work to it.
- Storms and wind temporarily affect the water level, so allow for them when planning observations.
Depth surveying step by step
A marine survey is normally carried out from a boat fitted with an echo sounder, a GNSS positioning unit and a motion sensor. The stages are:
- Plan parallel survey lines with a spacing suited to the level of detail required.
- Calibrate the echo sounder for the speed of sound in water, which varies with temperature and salinity.
- Record depths and positions simultaneously, correcting for boat motion.
- Apply the tide correction and merge the results with the land survey at the shoreline.
- Produce contour maps and a 3D model of the seabed.
Joining the marine and land surveys needs an overlap zone in the shallows, so no gap is left between what the boats cover and what the ground survey covers.
Using the results in design and monitoring
Depth data is used to place quays, set the depth of marina basins and navigation channels, and calculate dredging or fill quantities. Repeat surveys over time also reveal erosion or sediment build-up by comparing old and new surfaces, which helps judge how well breakwaters and channels are working.
- Analysing shoreline change between images and surveys from different periods.
- Calculating the volume of sand moved or accumulated in an area.
- Checking that completed works match the design levels.
Frequently asked questions
Is an aerial survey enough to define the shoreline?
It is useful for drawing the shoreline quickly, but the shoreline moves with the tide, so the time of the imagery and the reference level must be stated, and ground measurements added where needed.
What gets in the way of marine surveys in practice?
High waves, wind, water currents and rocky obstacles in shallow areas. Some sites need the work scheduled for calm days.
Why repeat the survey after construction?
Because sand movement can change once new structures are in place. Repeat surveys reveal accretion or scouring early, so maintenance can be carried out in good time.
