Humans have been exploring underwater for thousands of years, called seafloor mapping or bathymetric survey. Early methods used weighted cable or heavy rope lowered over a ship’s side until it reached the seafloor, making it slow and inaccurate. As technology advances, modern devices are now available in the market, like multibeam sonar equipment, which analyzes echo sounders’ data right on your vessel.
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What Is a Bathymetric Survey?
Bathymetry studies beds or floors of water bodies, including rivers, streams, oceans, and lakes. The term “bathymetric” originated from two Greek words, such as “bathys,” meaning “deep,” and “metrike,” which means “to measure.”
Also referred to as a fathometric survey, experts use a bathymetric survey to study and map the depth and shape of a water body. It allows them to view an exact representation of the seabed, including its elevations, any scour around submerged structures, and anomalies. It also inspects the surrounding tides, shorelines, currents, and waves to show the overall situation of the area.
Methods of Bathymetric Surveys
- Multi-beam surveying. A multibeam echo sounder is attached to a boat, mapping a swath of the seafloor under the ship. It sends out multiple, simultaneous sound waves in a fan-shaped pattern, which experts can read in real-time on their boats. This method is usually used in larger bodies of water.
- Single-beam surveying. Single-beam surveying measures the water depth directly under the boat, commonly used for smaller bodies of water.
- Sub-bottom profilers. Sub-bottom profilers are often used to view the layers of rocks and sediments under the floor of a water body. Experts use a transducer that penetrates and sends a sound wave to the bottom of a body of water. Then they map the returned sound waves to show the layers underneath the floor of the water body.
- Acoustic Doppler Current Profiler (ADCP). ADCPs measure how fast water moves across an entire water column. It is anchored to the seafloor to measure not only the current speed of the bottom but also the equal intervals until the surface.
- Ecomapper Autonomous Underwater Vehicle. Ecomappers can collect detailed bathymetric data in places hard to reach by boat, using side-scan sonar and a Doppler velocity log.
Purposes of Bathymetric Surveys
1. Planning and Construction of Dams, Docks, Harbors, and Other Marine Structures
Before a marine construction, experts need to ensure that the depth of the water in and around ports is enough for ships to enter and berth safely. Also, sea beds that support floating structures must have a strong foundation.
On the other hand, when constructing dams or other marine structures, engineers need adequate knowledge of the surrounding terrain to ensure the structure’s strength, using sonar for marine construction.
2. Help in Flood Control Systems
Bathymetric surveying helps experts to predict potential flooding zones so they can suggest safety measures that prevent disasters. They will study how the ocean floor changes around the coastline and correlate it to historical records of flooding and tsunamis.
3. Studies and Research
The government can determine the shorelines that extend around a coast through a bathymetric survey. They use these shoreline charts to conduct studies and research on the impacts of water bodies on land, as well as to identify the actual maritime border of countries. This data also helps countries in launching space shuttles and rockets.
4. Ship Navigation
Specific ocean routes have low depths or rocks and coral deposits that pose a danger to ships. So, bathymetric survey results are used in identifying the safest possible paths for vessels to take.
Dredging is the removal of sediments, debris, and rocks at the seabed of lakes, harbors, rivers, and other water bodies. Since sedimentation (gradual filling of channels and ports with sand and silt) naturally occurs, the shipping industry has to maintain or increase the depth of navigation channels, berthing areas, or anchorages for the safe passage of boats and ships. Bathymetric survey results are the basis for this process.
6. Pipeline System Installation and Maintenance
Before laying seabed pipelines, engineers must survey the bottom of the body of water to make sure that pipe tracks are constructed correctly. They use sonar pipeline inspection equipment to survey the surroundings where the pipes will be installed, the pipe itself, and the pipe surface.
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