MAPPING SEDIMENT AND WATER PROPERTIES IN A SHALLOW COASTAL ENVIRONMENT WITH AIRBORNE ELECTROMAGNETIC PROFILE DATA - CASE-STUDY - THE CAPE LOOKOUT, NC AREA

Airborne Electromagnetic profile (AEM) data has been demonstrated to p rovide good airborne measurements of shallow ocean bathymetry but has received limited use in very shallow coastal barrier island and estuar ine environments. This paper illustrates the utility of the AEM for de veloping maps of physical properties useful in characterizing sediment and water in these types of complex coastal environments. The test si te is the Cape Lookout area at the southern end of North Carolina's Ou ter Banks. Inverse methods were applied to a two-layer model to calcul ate water depth, water conductivity and sediment conductivity values f rom transect data. These calculated model parameters were then used to develop interpolated spatial maps for these variables. The analysis p rovided generally good agreement between the map values and ground tru th. The water depth model, used to generate a bathymetric map, fit the actual data points very well and much better than the initial sedimen t and water conductivity models that required additional filtering to produce good spatial maps. The sediment conductivity maps corresponded fairly well with known shallow sediment types and the water conductiv ity maps demonstrated the expected variation in an estuarine environme nt such as this. Spatially the maps depict very good general trends fo r the variables studied as well as identifying some special areas of i nterest at a more detailed scale. An understanding of the spatial dist ribution of these sediment and water variables has broad utility in a variety of physical and biological coastal process models.