Monitoring Beach Morphology Changes Using Small-Format Aerial Photography and Digital Softcopy Photogrammetry

¹ U.S. Geological Survey, 345 Middlefield Rd., MS 999, Menlo Park, CA 94025

Cheryl Hapke currently works for the U.S. Geological Survey, Coastal and Marine Geology Program in Menlo Park, California, as a photogrammetric coastal geologist. Ms. Hapke previously worked with the Natural Hazards Mapping Program at North Carolina State University, Department of Civil Engineering. She earned an undergraduate degree from the University of Pittsburgh (1985, Geology), a Masters Degree from the University of Maryland (1992, Geology), and undertook additional post-graduate studies at Duke University. She is currently pursuing her Ph.D. at the University of California, Santa Cruz in Coastal Geology. Hapke's research focuses on the applications of aerial photography and digital softcopy photogrammetry to the study of coastal evolution and processes in a variety of geological settings including barrier islands and cliffed beaches.

Dr. Richmond is a research geologist with the U.S. Geological Survey (USGS) Coastal and Marine Geology Program in Menlo Park, California. Dr. Richmond has spent the last 20 years with the USGS working on coastal geology of mid- and low-latitude sedimentary environments. He received his M.S. degree from Waikato University in Hamilton, New Zealand, and his Ph.D. from the University of California, Santa Cruz. His current research involves examining the coastal impacts of the 1997–1998 El Niño along the U.S. West Coast and beach loss in the Hawaiian Islands.

ABSTRACT

Current methods of monitoring beach morphology changes commonly involve the establishment of Global Positioning System profiles that are surveyed on a regular basis. Although this method produces precise measurements of coastal topography, it is costly in time and effort and may result in large data gaps between profiles. Much of our understanding of coastal dynamics is thus limited by profile spacing and survey frequency. Softcopy photogrammetry is increasingly being used as an alternative to assess shoreline change and study beach morphodynamics. This method of producing three-dimensional topographic models and orthophotographs from digitized aerial photography can aid in filling in the gaps between established profiles. A limiting factor to this technology is the cost of obtaining high-resolution aerial photography.

We have developed an aerial mapping system designed to collect data in an efficient and cost-effective way. We use a small-format aerial photography system that can be mounted on a variety of small aircraft on short notice. After a flight, the photographs are scanned, and softcopy photogrammetry software is used to create both DTMs (Digital Terrain Models) and orthophotographs. The DTMs can be compared with existing profiles for accuracy, and volumetric changes can be computed. The orthophotos are used to make precise measurements of the position and morphology of shoreline features. This aerial mapping system is advantageous over previous methods of beach morphology change monitoring because it allows for rapid response to storm events and provides a cost-effective method of establishing a continual monitoring program in erosion hazard areas.