REDUCTION OF MAINTENANCE BY PROPER ORIENTATION OF SHIP CHANNELS THROUGH TIDAL INLETS

Abstract

The inherited courses of some hay-port ship channels take them through tidal inlets along courses running across dominant directions of strong current movement and scour, or on courses that upset the natural tidal regimes. Such discordance may make necessary excessive maintenance dredging. Geological study of a section of the Texas coast shows that, in a unit coastal environment, there may he a predictable stahle position of a tidal inlet and a common stahle orientation for its channel which might better have been used for the ship channel outlet. Among probable damages to the natural environment resulting from a wrong orientation is excessive sedimentation in the inlet channel. Engineering studies are needed to determine the economics of reorientation and relocation of misfit channels of the type described. The tidal inlet or "pass" is the central channel of a tidal delta. The delta is an enlargement of a barrier sand island at a gap where tidal and other flow into and out of large inland water bodies forms a strong local field of force with a longshore sediment drift and current. Engineering works in this field of force should utilize its characteristics, not fight them. As the coastal section studied here is only one of many, extension of the geologic study, with accompanying engineering studies, should be made to permit general laws of inlets, tidal deltas and barrier islands to be set up for both geology and engineering.