Facts About Underwater Surveys

The International Association of Dredging Contractors (IADC) has just published a new ‘Facts About’ publication on underwater surveys.

‘Facts About’ is a series of concise, easy-to-read leaflets which give an effective overview of essential facts about specific dredging and maritime construction subjects.

Each leaflet provides a kind of ‘management summary’ for stakeholders who need a quick understanding of a particular issue.

The leaflets are part of IADC’s on-going effort to support clients, consultants and others in understanding the fundamental principles of dredging and maritime construction because providing effective information to all involved parties is an essential element in achieving a successful dredging project.


Surveying is the science of accurately determining the area of any portion of the Earth’s surface, be it on land or underwater.

The general aim of surveying is to measure and fix a position in three dimensions. Underwater or hydrographic surveys are part of the data collection process used during dredging and maritime infrastructure works to establish the seafloor and subsea conditions and monitor dredging accuracies.

Surveying is an essential element and a prerequisite in the planning and execution of nearly every form of construction project including maritime and dredging projects.

Nowadays data can be stored on computers and shared, providing crucial information to dredging contractors and their clients.


Surveying is indispensable in the modern dredging industry. Surveys are used to collect data about navigable waters – including oceans, seas, lakes and rivers – in order to ensure navigational safety. Port authorities, for instance, are charged with guaranteeing safe and accurate navigational depths so surveying the port and access channels is crucial.

Surveys are used to gather data for capital (new projects) as well as maintenance dredging where they help determine the total amount of soil which must be removed. Surveys are used to check if the design depth is reached over the entire area.

Surveys are also used in the offshore industry from the initial design to follow-up inspections of the completed subsea gas or oilfield infrastructure. For instance, whilst trenching and backfilling operations for pipeline laying the trenches can be measured to ensure the proper profile has been made in which to lay the pipe.

Afterwards the accuracy of backfilling with rock can be monitored.

For the complete publication, click here.