SHEAR-DRIVEN FLUSHING OF MICRO-TIDAL MARINAS

Abstract

Flushing or residence times are typically used as a first step in assessing water quality in marinas, harbours and coastal basins. Recent publications have offered guidance in relation to optimal marina basin and entrance geometries to help achieve rapid renewal. However, these guidelines have been developed for the particular case where water exchange is strongly tide-driven and are not widely applicable, particularly in micro-tidal regions. Where water renewal rates are dominated by shear-driven circulation and lateral transfer of momentum at the interface between the marina and the adjacent water body (i.e. a mixing layer), there is a strong analogy to groyne fields and other cases involving flows containing quasi-stagnant peripheral areas (dead zones). A series of numerical hydrodynamic models, developed in the TELEMAC system, were used to investigate the potential for the dead zone model of water exchange to provide a
 better means to guide optimization of basin and entrance geometry under such conditions. Real-world marina case
 studies were used to identify any constraints affecting the practical implementation of such an approach. The numerical model results demonstrate particular conditions under which the dead zone model of water exchange can be used effectively to optimize marina basin and entrance geometry.