Band 9: The diagram below shows how a dredger can remove mud from the bottom of canals. The table compares features of the canal dredger with those of a coastal dredger. Summarise the information by selecting and reporting the main features and make comparisons where relevant.

The diagram illustrates the operation of a dredging system for removing mud from canal beds, while the accompanying table presents a comparison between canal and coastal dredger specifications.

It can be clearly seen that there is a new type of quiet dredging boat being used in Venice. It eliminates the need for complete canal drainage during maintenance and at the same time the system comprises a main boat fitted with hydraulic arms that deploy a pump with rotating blades to the canal bottom. Extracted mud is pumped as slurry through a large tube to the shuttle vessel, which transports the waste material outside the city limits for dumping.

As evidenced by the table, coastal dredgers significantly surpass their canal counterparts in size and capacity. The coastal variant measures 85 meters in length – nearly four times longer than the 22-meter canal dredger – and has a hull breadth of 14 meters compared to 6.69 meters. Coastal dredgers operate at depths up to 35 meters, whereas canal dredgers function in just 1.87 meters of water. The operational areas also differ markedly, with canal dredgers confined to canals and lagoons while coastal versions service the open waters of the North Sea.

While both dredger types follow similar mechanical principles, the canal version represents a scaled-down adaptation designed for the limited space in urban waterways.