RATES AND PATTERNS OF COASTAL EROSION FOR THE PANAMA VIEJO HISTORICAL AND ARCHEOLOGICAL SITE

The Panama Viejo Historical and Archeological Site, the location of the oldest colonial city on the Pacific Ocean, is located on the Gulf of Panama in the south-central region of the Republic of Panama. Panama Viejo is built on coastal bar and fluvial sediments and pyroclastic rock bordering a shallow cove. These marine, fluvial, and volcanic sediments that underlie historical Panama Viejo are prone to mechanical wave erosion, especially on those parts of the shore exposed to the dominant NNE winds. As such significant erosion and subsequent shoreline retreat have occurred since the city of Panama Viejo was first established almost 500 years ago, yet there are no quantitative estimates of rates and the extent of coastal erosion during this time period. It was the purpose of this study, therefore, to estimate the extent and rates of historical (~1500 AD - present) coastal erosion and to estimate current trajectories of coastal erosion for the Panama Viejo site. Towards that goal we use aerial imagery and historic map data formatted into a GIS environment to 1) calculating the temporal and spatial distribution of coastal erosion for historical Panama Viejo since its first establishment 500 years ago up to modern times, 2) extrapolating patterns and rates of erosion, for purposes of archeological reconstruction, for pre-colonial Panama Viejo, and 3) calculate present-day trajectories of future coastal erosion for the general area surrounding the historical site. We find that much of the historical boundaries of Panama La Vieja once extended 100 meters or more seaward of the present day shoreline, these shoreline areas having eroded due to mostly natural wave-driven erosion, while other parts of the coastal area have prograded seaward and choked entire bays with fine grained sediments eroding from the upstream reaches of the drainage basin, likely in response to anthropogenic activity.