Mapping shoreline vulnerabilities using kite aerial photographs at Oluvil harbour in Ampara

Abstract

The dynamics of coastal ecosystem are mainly controlled by nearshore processes, coastal geomorphology and human induced land-use changes. A rapid change of coastal shoreline due to harbour construction in Oluvil, which is in Ampara district caused a serious coastal erosion scenario. This study examines the coastal microtopography in relation to high resolution digital elevation models, coastal vegetation bioshield mass, and sea level rise. A Kite Aerial Photography (KAP) platform was created using two light-weight automatic cameras with dual bandpass Red-NIR filters, a Picavet stabilizing rig, a GPS tracker and a parafoil kite. The KAP images with high resolution were acquired at 15 m altitude and the data was processed to build mosaic images, orthorectified and georeferenced DEMS using Agisoft PhotoScan (structure-from-motion) and ENVI software. Oluvil beach habitat vulnerabilities were mapped using Normalized Difference Vegetation Index (NDVI) for vegetation bioshield mass estimation, Digital Elevation Model for sea level rise and coastal land-use changes using historical images. The image processing produced a point cloud with an average density of 20 points/cm2; a DEM with 2 cm resolution; and an orthophoto mosaic with an average resolution of 0.5 cm. The NDVI and historical images showed a significant vegetation reduction over time. With subsequent negative impacts of coastal vulnerability such as flooding due to sea level rise. The objective of this study is to assess the vulnerabilities in Oluvil coastal beach habitats in terms of coastal erosion, sea level rise and vegetation biosheild mass and health. This work utilized KAP which has a great potential to bridge science with high spatial/temporal resolution in-situ data for monitoring coastal habitat vulnerabilities, and can be used for sustainable land management prior to implement any development or construction program.