Stirring up Trouble? Resuspension of Bottom Sediments by Recreational Watercraft

ABSTRACT

An experimental and theoretical study of the hydrodynamic impacts of recreational watercraft in shallow water bodies is presented. Of particular interest is the ability of turbulent prop or jet wash to resuspend bottom sediments. Intuition suggests, and the experiments confirm, that this ability is a strong function of boat speed and water depth.

The results of this study demonstrate that boats operating at high speed have no greater impact on the lake bed than boats travelling at idle speeds. The greatest impact is seen when boats are travelling at ‘near-plane’ speeds. This critical speed is a function of boat size and water depth.

To increase the usefulness of the observations, a theoretical model of the flow underneath a passing boat was developed and validated with the data. Relying on only a few input parameters, the model can be used to estimate, for example, the minimum operating depth required for a given boat to prevent sediment resuspension.

Discussion of the relevance of this work in the context of setting use restrictions for watercraft is provided.

Key Words:

• boating
• recreational conflicts
• sediment resuspension
• hydrodynamics