DREDGING FOR FLOOD-RISK REDUCTION UNDER CLIMATE CHANGE: A CRITICAL REVIEW OF HYDRAULIC, SEDIMENT AND ENVIRONMENTAL CONSIDERATIONS

Summary

Dredging is widely used to restore channel capacity, but its contribution to climate-resilient flood-risk reduction depends on whether sediment-induced loss of conveyance is a principal flood mechanism. This critical narrative review synthesizes evidence on climate-driven flood hazards, channel hydraulics, sediment dynamics, riverine and coastal dredging, environmental impacts, beneficial sediment use and integrated flood-risk management. The review examines how channel geometry, flow conditions, downstream boundary levels, tributary inflows, floodplain connectivity, tidal processes and re-sedimentation influence the effectiveness and durability of dredging. Evidence indicates that targeted sediment removal can increase channel conveyance and reduce water levels for specified discharges where deposition constrains hydraulic performance. However, benefits are context-dependent, and extensive dredging may alter tidal propagation, redistribute flood risk or produce only temporary improvements where sediment rapidly accumulates. Environmental concerns include turbidity, habitat disturbance and contaminant remobilization, although suitable dredged material may support wetland restoration and shoreline nourishment. The review proposes an evaluation framework integrating baseline channel geometry, hydraulic modelling, flood levels and inundation, sedimentation rates, environmental indicators and life-cycle impacts. For Nigeria and comparable settings, dredging decisions should be based on the dominant flood mechanism, downstream consequences and long-term maintenance requirements. Dredging is therefore best treated as a targeted component of integrated flood-risk management rather than a universal standalone flood-control measure.

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