Hypsometry of estuaries, creeks and breached sea wall sites

The way in which the plan area of a drainage basin varies with elevation, is known as the hypsometry and is a useful way of capturing key elements of the geomorphological form. Variations in this form can alter the way the tide propagates and change the ebb and flood properties of the tide. The hypsometry can be particularly relevant where a sea wall is to be breached to create new mudflat and saltmarsh within a managed re-alignment site. A number of parametric relationships are examined and used to fit data obtained from bathymetry and topography for a range of estuaries, creeks and breached sea wall sites. These results are used as the basis for a method to characterise the hypsometry of inlets and breached sea wall sites. This is particularly useful for the design of breaches in managed re-alignment sites because the hypsometry has a major influence on the rate of infilling and hence the size of breach required to avoid scour problems. It also provides an indication of the likely habitat composition of the site ranging from mudflat to saltmarsh to supra-tidal.