USGS and Woods Hole Oceanographic Institution Participate in Coastal Erosion Workshop in Ghana


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USGS and Woods Hole Oceanographic Institution Participate in Coastal Erosion Workshop in Ghana

By Cheryl Hapke and Andrew Ashton (WHOI)
May 2009

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Above: Coastal Erosion Workshop participants at the University of Ghana. Dr. George Wiafe (front row, third from left, between Andrew Ashton and Cheryl Hapke) is the Chair of the Department of Oceanography and principal investigator of the Coastal Erosion Studies project at the University of Ghana. Dr. Augustus Vogel (back row, far left) is the Maritime Partner Liaison for the Africa Partnership Station. [larger version]

Erosion is a chronic issue along the Ghanaian coastline, where high erosion rates are affecting coastal infrastructure and valuable cultural resources. Nearly 50 percent of the population of Ghana lives along the coast, and erosion rates as high as 1 m/yr have been measured near the country's capital city, Accra. The geomorphology of the coastline varies widely—from coastal lagoons with barrier beaches, to rocky cliffs fronted by narrow beaches, to a large wave-dominated deltaic system. Human intervention along the coastline has not been conducted in a systematic fashion, and attempts at erosion mitigation range from small rock revetments scattered along the coast to a large engineering project (the Keta Sea Defense) along the Volta River delta in the eastern part of the country. Large-scale infrastructure development, including damming of the Volta River and the construction of deep-water harbors, has disrupted the natural movement of sediment along the beach and nearshore (the "littoral" zone) and delivery of sediment to the coast. Researchers at the University of Ghana are in the initial stages of developing a comprehensive monitoring and assessment program to understand the processes driving coastal erosion in Ghana; however, the varying geomorphology and intermittent human modification present unique challenges to developing a systematic strategy.

The Africa Partnership Station, an international initiative supported by U.S. Naval Forces Africa, works with U.S., European, and African partners to enhance maritime safety and security on the African continent. Through funding from the Coastal Geosciences Program within the U.S. Office of Naval Research and with assistance from the Africa Partnership Station, researchers at the University of Ghana are partnering with U.S. scientists to examine and understand coastal processes, as well as to develop a monitoring network to identify future coastal hazards. As part of an initial effort, Cheryl Hapke from the U.S. Geological Survey (USGS) and Andrew Ashton from the Woods Hole Oceanographic Institution (WHOI) traveled to Ghana to meet and collaborate with scientists from the University of Ghana.

Above: Coast of Ghana. The workshop was held in Accra at the University of Ghana. Field-trip and data-collection sites included a beach near Tema and several locales near Keta. [larger version]

A 5-day Coastal Erosion Workshop was held February 23-27, 2009, at the Department of Oceanography and Fisheries at the University of Ghana in Accra. In addition to Hapke and Ashton, participants included faculty and graduate students from the Departments of Oceanography, Geology, and Physics at the University of Ghana, as well as researchers from Kwame Nkrumah University and several government agencies. Part of the effort was not only to meet and share information and ideas but also to visit specific field sites of interest to collect initial surveys and develop data-collection strategies. The Department of Oceanography has recently acquired real-time kinematic Global Positioning System (RTK GPS) instrumentation, and Ashton brought along a ground-penetrating radar (GPR) system to demonstrate how long-term coastal evolution can be recorded in the sedimentary record. Participants spent 3 days in the field at Mukwe Beach near Accra, and Ada Foah, Cape Saint Paul, and Keta in eastern Ghana. During the final day of the workshop, Hapke and Ashton met with principal investigator and Department of Oceanography Chair George Wiafe and faculty members Selorm Ababio and Appeaning Addo to discuss specific scientific issues and directions that might lead to fruitful collaborations. The smaller group drafted an abstract about the Coastal Erosion Program at the University of Ghana that will be presented at the International Geoscience and Remote Sensing Symposium in Cape Town, South Africa, in summer 2009.

Above left: Cheryl Hapke talks with Selorm Ababio (University of Ghana) about coastal-erosion issues at Mukwe Beach, near Accra. Soft bluffs composed of Quaternary sediments are eroding rapidly at this site. [larger version]

Above right: Workshop participants collect ground-penetrating radar (GPR) data under the guidance of Andrew Ashton (second from right) at Ada Foah. The GPR data indicate a long history of beach progradation in this area, likely associated with formation of the Volta Delta. High rates of erosion in more recent times are likely due to the disruption of sediment supply caused by damming of the Volta River. [larger version]

Above left: Workshop participants set up a real-time kinematic Global Positioning System (RTK GPS) base station and roving unit at Ada Foah at the beginning of a beach survey. [larger version]

Above right: A colonial town built at this location in the 1930s has been abandoned, largely due to erosion, which is undermining a cemetery and building foundations shown here. [larger version]