Reducing Harbor Siltation. I: Methodology

Abstract

This paper describes a decade of research on siltation-reducing measures for harbor basins and the methodology and measuring techniques developed. A classification of harbor systems is made on the basis of siltation mechanisms, i.e. horizontal entrainment by mixing layers, tidal filling, and density currents. This classification distinguishes between harbors in various environments, i.e. stagnant water systems such as shallow lakes, where wind-induced currents prevail, riverine systems, tidal systems, either homogeneously fresh or saline, and estuarine systems with fresh/salt water induced density gradients. Case studies and detailed design studies yielded large reductions in siltation rates of many tens of percents for all harbor basins located in flowing water systems, using a variety of siltation-reducing techniques. These reductions were attained by reducing the exchange flow rates between the harbor and ambient water, and by reducing the sediment concentration of the water entering the basin. In the case of stagnant water systems with very fine, mainly organic matter, a reduction in exchange flow rate cannot be successful, and a reduction in siltation rates can only be achieved through the prevention of dead water zones in the harbor basins. The methodology developed is cost efficient and therefore applicable for large commercial ports as well as small marinas.