Bathymetry Survey: Uses and How It Is Done

More than 70% of water bodies cover the planet. Have you ever wondered how dams, docks, and other marine constructions are built?

Humans have been exploring underwater for thousands of years, called seafloor mapping or bathymetric survey. They used heavy cable or rope lowered over their ship’s side until it reached the seafloor, resulting in inefficiencies. As technology advances, experts now use modern devices, such as multibeam sonar equipment that analyzes echo sounders’ data right on their boats. 

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” that means “deep,” and “metrike,” which means “to measure.” 

Also referred to as a fathometric survey, a bathymetric survey lets experts study and map the depth and shape of a body of water. It shows an exact representation of the seabed, including its elevations, any scour around submerged structures, and irregularities. 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. Engineers use a multibeam echo sounder attached to a boat that maps a swath of the sea bed under their ship. The device sends out multiple, simultaneous sound waves in a fan-shaped pattern, which they can read in real-time on the boat. This method is usually used in larger bodies of water. Visit this page for more info.
  • Single-beam surveying. This method measures the water depth directly under the boat, often used for smaller bodies of water.
  • Sub-bottom profilers. Sub-bottom profilers are used to view the layers of rocks and sediments under the floor of a water body. Engineers use a transducer that penetrates and sends a sound wave to the water body floor. Experts then map the returned sound waves to show the layers underneath the base of the water body.
  • Acoustic Doppler Current Profiler (ADCP). An ADCP is an instrument that measures how fast water moves across an entire water column. It is secured to the seafloor to measure the current speed of the bottom and equal intervals until the surface.
  • Ecomapper Autonomous Underwater Vehicle. Ecomappers can collect detailed bathymetric data in places that are difficult to reach by boat. They use side-scan sonar and a Doppler velocity log. 

Purposes of Bathymetric Surveys

1. Planning and Construction of Dams, Docks, and Harbors

Experts need to ensure that the depth of the water in and around ports is enough for ships to enter and berth safely. The sea beds that support floating structures should also have a strong foundation. 

On the other hand, engineers need adequate knowledge of the surrounding terrain to ensure the structure’s strength with sonar for marine construction when constructing dams or other marine structures.

2. Help in Flood Control Systems

Bathymetric surveying helps experts 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

Through surveying, the government can identify the shorelines that extend around a coast. They use these shoreline charts to conduct studies on the effect of water bodies on land and determine the actual maritime border of countries. This data also helps countries in launching space shuttles and rockets.

4. Ship Navigation

Bathymetric survey results are used to help identify the possible paths that a vessel can safely take since some ocean routes may have rocks and coral deposits or low depths that pose a danger to ships. 

5. Dredging

Dredging is the removal of sediments, debris, and rocks at the seabed of lakes, harbors, rivers, and other water bodies. Sedimentation or the gradual filling of channels and ports with sand and silt naturally occurs, which can lead to safety threats to ships. That’s why the shipping industry needs 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 need to conduct an underwater survey with sonar for pipeline inspection. This lets them view the surroundings where they install the pipes, the pipe itself, and the pipe surface to ensure the pipe tracks are constructed properly. The survey is continuous for maintenance and repair.