HYPSOGRAPHIC ANALYSIS OF COASTAL BAY ENVIRONMENTS USING INTEGRATED REMOTE SENSING TECHNIQUES. GREAT MACHIPONGO BAY. VIRGINIA. U.S.A

摘要

Coastal bays provide protected environments for numerous species. The environmental quality of these environments is strongly dependent on the depth and exchange of water over different parts of the basin floor. It is known that the floors of most coastal bays and lagoons do not have uniform depths with smooth surfaces. Variations in depth are linked to the complex hypsographic characteristics of a relict antecedent surface. Some of the most productive benthic environments are shallow tidal and subtidal flats. Accurate surveys of these areas are generally not available for many of these areas since they are inaccessible for most survey boats and most surveys are conducted for providing aids for navigation. In coastal bays, most areas that are too shallow for navigation are described as tidal flats or changeable areas. However, subtle differences in depth often determine the light limitations for primary production. At larger scales, the relationship between water level and the hypsometry of a bay determines rates and patterns of flushing. A need for accurate surveys of shallow bays resulted in the development of a rapid technique that could produce horizontal accuracy of 5-10 meters and vertical accuracy of 0.33 meters. Differential GPS data provided the horizontal data requirements for display on Landsat imagery. Echosounding provided the vertical precision that could be accurately adjusted to a NAD 1927 USGS datum.