3.5.1. Dredging and River Widening

Dredging is the removal of sediment from the rivers and harbors. It can be done by hydraulic (e.g., by a "suction hedger") and mechanical methods (e.g., a "bucket dredger"). Environmental regulations increasingly require the cleaning of contaminated dredged material and the safe disposal of dredged material in controlled deposit areas. Therefore, dredging costs are increasingly associated with both the excavation, treatment, and disposal of dredged material. Costs for mechanical dredging in the United Kingdom vary between \$44 and \$59/m3, whereas suction dredging is cheaper at \$13/m3—both including the cost of disposal [78]. Costs for mechanical dredging and transport only in The Netherlands are estimated at \$15–19/m<sup>3</sup> [79], which indicates that the storage of frequently contaminated material is relatively expensive. Costs for dredging in Bangladesh are estimated at ~\$2/m<sup>3</sup> [80].


**Table 7.** Costs for channel management, and nature-based solutions for riverine systems.
