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Water Injection Dredging is a hydrodynamic dredging

technique that should be taken into consideration as a

cost-effective, environmentally sound solution to some

specific dredging operations. Dredging works can be complex

and costly, accounting for a substantial proportion of the

budget of a maritime project. To effectively plan and execute a

dredging operation, to be able to select the most appropriate

dredging plant, requires extensive knowledge of the material

to be dredged as well as the environmental circumstances of

the site to be dredged. Since the mobilisation and capital costs

of dredging plant are quite significant, choosing the wrong

vessels and methods can have severe economic consequences.

Appropriate ground and environmental surveys are

fundamental to the success of dredging operations, from both

a technical and an economic perspective. Water Injection

Dredging has very specific limitations but in the appropriate

situation it also has very specific benefits.

Why Water Injection ?

WATER INJECTION DREDGING

Water Injection Dredging is a relatively new hydrodynamic

dredging technique, developed by engineer R.N. Van Weezenbeek a little more than 25 years ago, which has been gradually gaining popularity for maintenance dredging.

Since port authorities are continually confronted with the siltation of the harbours and access channels, regular maintenance dredging is a necessity to ensure safe navigation depths in these waterways. However, especially for smaller ports, the financial demands of dredging can become burdensome.

Generally speaking the larger the port project, the more

cost-efficient dredging becomes using traditional dredging

techniques – trailing suction hopper dredgers and cutters for

instance. But for the regular maintenance of smaller harbours,

the technology of Water Injection Dredging can be an

effective, economical and environmentally sound solution.

What is Water Injection Dredging ?

How does Water Injection Dredging work ?

Water Injection Dredging is a technique in which a specially

developed Water Injection Dredger injects large volumes of

water at a low pressure into the sediment, using pumps with

a series of nozzles on a horizontal jetbar. This fluidises the

sediment by effectively overcoming the cohesion in fine grained

(cohesive) soils or internal friction of coarse-grained

(granular) soils. This fluidised sediment then remains close

to the river or channel bed, flowing down to deeper areas.

Fluidised soil is also sometimes referred to as fluid mud,

fluid bed or density cloud, but since the sediment remains

just above the bed, the term “fluidised soil layer” is generally

agreed to be a more apt description.

Staying close to the bed creates a density current that

then, either by the force of gravity or through a natural or

artificially created slope, flows downwards to deeper water.

This all occurs with a minimum of disturbance to the

equilibrium of the ecosystem. In this way, instead of

mechanical transportation, nature takes care of the sediment

transport, making Water Injection Dredging under certain

conditions a very cost-efficient dredging technique.