1 TopCAT – Topographical Compartment Analysis Tool to analyze 2 seacliff and beach change in GIS 3 4 Michael J. Olsen1*, Adam P. Young2, and Scott A. Ashford1 5 1. School of Civil and Construction Engineering, Oregon State University 6 2. Scripps Institution of Oceanography, University of California, San Diego 7 8 *corresponding author 9 220 Owen Hall 10 Corvallis, OR 97331 11 +1 (541)737-9327 12
[email protected] 13 14 15 Abstract 16 This paper discusses the development of a new GIS extension named the Topographic 17 Compartment Analysis Tool (TopCAT), which compares sequential digital elevation models 18 (DEMs) and provides a quantitative and statistical analysis of the alongshore topographical 19 change. TopCAT was specifically designed for the morphological analysis of seacliffs and 20 beaches but may be applied to other elongated features which experience topographical change, 21 such as stream beds, river banks, coastal dunes, etc. To demonstrate the capabilities of TopCAT 22 two case studies are presented herein. The first case examines coastal cliff retreat for a 500 m 23 section in Del Mar, California and shows that large failures comprised a large portion of the 24 total eroded volume and the average retreat rate does not provide a good estimate of local 25 maximum cliff retreat. The second case investigates the alongshore volumetric beach sand 26 change caused by hurricane Bonnie (1998) for an 85 km section in the Cape Hatteras National 27 Seashore, North Carolina. The results compare well (generally within 6%) with previous 1 28 investigations. These case studies highlight additional information gained through performing a 29 detailed, discretized analysis using TopCAT.