Mechanical Dredging vs Hydraulic Dredging: Which is Better?
- Ian
- Dec 15, 2025
- 4 min read
Dredging is the practice of removing sediments and debris from the bottom of lakes, rivers, harbours, and other water bodies. Over time, sediments like sand and silt are carried by waterways downstream. Sedimentation gradually fills up the water body, decreasing its depth, and creating challenges for navigability and increasing the risk of flooding.
But removing the enormous amount of material from waterways comes with several challenges. Dredging uses specialised equipment to scoop, suction, and remove underwater sediments.
There are two main techniques: mechanical dredging and hydraulic dredging. The former literally digs and excavates the sediment, while the latter relies on suction and pumps to move the sediment as slurry. But which is better? And what are the advantages and disadvantages of each?
In this article we'll discuss:
What is Mechanical Dredging?
Mechanical dredging involves physically digging the sediment from the bottom of the waterway. Mechanical dredging equipment includes clamshells, backhoes, and draglines to excavate and move the material.
Once it’s excavated, the sediment and other debris are loaded onto barges and workboats. It’s then transported to a truck for disposal. Mechanical dredging equipment can be based on land or fitted onto pontoons and barges. This allows teams to dredge in hard-to-reach locations.
Generally, mechanical dredging is recommended for sand, gravel, and other dense, compacted materials. The diggers can easily excavate this material, and it’s readily transported via barge or truck.
Advantages of Mechanical Dredging
Strong enough to shift tough, compacted material like clay, rubble, and gravel without struggling.
Perfect when you need control and accuracy, especially around docks, marinas, and narrow canals.
Material is lifted out directly, so you can see exactly what’s being removed and where it’s going.
Disadvantages of Mechanical Dredging
Stirs the water up more than pumping methods, which can make the area cloudy during work.
Takes longer if you’re dealing with very large volumes.
Needs space for cranes, barges, and machinery, which isn’t always available on tight sites.
What is Hydraulic Dredging?
Hydraulic dredging relies on suction and pumps to move sediments as slurry — a mixture of solids and liquids. The slurry is pumped out via pipelines to be either distributed onto the surrounding land or removed to another location.
This method is recommended for sand and silt, where the material is fine and easily mixed with water. If the material is too heavy, pumping simply won’t work.
Despite its speed and effectiveness, a major downside is the amount of equipment needed: dewatering facilities, pumps, and more. This restricts its potential in low-access sites where space is minimal. Plus, it can be hard to transport the equipment. However, once it is set up, it’s by far the best option.
Hydraulic dredging is primarily used for river maintenance where the volume of material is high and often quite fine.
Advantages of Hydraulic Dredging
Clears large areas quickly by working continuously instead of in lifts or loads.
Causes less disruption to wildlife and the surrounding water while work is underway.
Can move material over long distances without needing fleets of boats or vehicles.
Disadvantages of Hydraulic Dredging
Not ideal for heavy or compacted ground, which can block or slow the system.
You’ll need somewhere to separate water from the dredged material once it’s pumped out.
More involved to set up, particularly for short or simple jobs.
Mechanical vs Hydraulic Dredging
Mechanical and hydraulic dredging might achieve the same result, but they’re very different techniques. The choice between them depends on the type of project and the material you’re moving.
As mentioned, the primary difference is the type of material they move:
Mechanical dredging is best for heavier, coarser material, where clamshell buckets and draglines can lift and remove a lot of material in one go.
Hydraulic dredging is best for finer material like sand or silt that can be mixed with water and pumped out.
The other big difference is price. Mechanical dredging is generally more cost-effective for smaller or complex jobs. Hydraulic dredging incurs a high setup cost but becomes economical the more material you’re removing.
Here’s an overview of the two options:
Area | Mechanical Dredging | Hydraulic Dredging |
How it works | Material is physically lifted out using buckets, grabs, or excavators and loaded onto barges or vehicles | Sediment is loosened and pumped away as a mixture of water and material through pipelines |
Best suited for | Heavy, compacted ground, debris, clay, and gravel | Sand, silt, and soft sediment in rivers, lakes, and channels |
Speed & scale | Slower but more controlled, better for smaller or precise jobs | Faster for large areas thanks to continuous pumping |
Accuracy | Highly precise and well-suited to tight spaces like docks and marinas | Less exact around edges but efficient in open water |
Impact on water | Creates more visible disturbance and clouding | Generally causes less disruption while work is underway |
Disposal & logistics | Material is removed and transported directly | Requires space for pipelines and drying or processing areas |
Setup complexity | Quicker and simpler to mobilise | Needs more planning and supporting equipment |
Choosing the Right Method for Your Project
When deciding between mechanical and hydraulic dredging, there are a few questions to ask:
What are the site conditions? Can you set up hydraulic dredging equipment, or is access limited?
What kind of sediment are you removing? Fine or coarse?
How big is the project? Is it worth the expense of setting up hydraulic dredgers? Days or weeks?
What are the environmental restrictions? Do you need to operate with a small footprint or not?
Answering these questions can help narrow down your choice. Sometimes, a hybrid approach is needed. Maybe there’s a layer of gravel in one section that needs removing before the hydraulic team can come in and pump out the rest.
If you’re curious about how The Rothen Group can help, explore our dredging techniques to learn more about how we work. Contact us today to talk through your project and get a quote for a dredging operation.