SEGUIN ISLAND, MAINE: THE USE OF DIGITAL MAPPING TECHNIQUES IN ENVIRONMENTAL ANALYSIS

Digital mapping techniques were used to survey the physical, topographic and cultural features of Seguin Island, Maine. Seguin Island is a unique coastal island environment, having suffered intense human impact for two centuries and then recently left undisturbed. The data collected was compiled in ArcGIS to provide detailed educational materials on island history, geologic significance, and environmental stewardship. These materials contain the latest and most complete mapping of the island, and provide a new data resource for use in planning and conservation. Seguin Island is a 25.6 hectare island located approximately 3km south of the mouth of the Kennebec River at the center of a heavily traveled waterway. It is home to the second oldest lighthouse in Maine, commissioned by George Washington in 1795. The operation of the lighthouse required a small resident population, the delivery and storage of raw materials such as oil, wood, and coal as well as regular island burnings. In 1985, the Coast Guard automated the lighthouse, eliminating the need for a resident keeper. Subsequently, the island has turned from a pivotal navigation aid in notoriously dangerous waters, to a rarely-visited, but publicly-accessible natural environment. This transition provides insight into the effects of a rapidly declining population and an emergence of a less impacted island ecosystem. In 1986 a non-profit organization, Friends of Seguin Island, was established to preserve the historic island. Digital mapping techniques using GPS and total station were used to map the complex topography with nearly 50 m of relief, including inaccessible steep slopes. Vegetation zones were mapped from high resolution digital aerial imagery as forest, grass, and shrubs, with shrubs being the dominate zone. Over 75 different plant species were observed. Structural data about geologic features was gathered, including steeply-dipping metamorphic layers with complex folding, and deformed granite intrusions. In addition, locations of general points of interest such as ~2 km of trails, scenic lookouts, lighthouse, tramway and outbuildings were recorded using a combination of handheld GPS and aerial imagery. The data collected provides a baseline digital data set, recording all aspects of the island's current conditions in order to evaluate future use.