ANALYSIS OF DESTRUCTIVE MAREJADAS AT THE BEACHFRONT COMMUNITY OF CEDEÑO, GULF OF FONSECA, REPUBLIC OF HONDURAS

News reports on a series of waves that severely damaged almost 100 beachfront structures in early September 2002 suggested that this unfortunate event was due to earthquakes or another unusual tectonic or underwater process. Investigations by the Comisión Permanente de Contingencias (COPECO) of Honduras proved otherwise. COPECO’s field representative, on site within 24 hours of the first high waves, observed the third episode of high wind waves superimposed on high tide. Waves approached parallel with the beach, heavy rip current action was evident, and some waves topped the berm crest, washing sand into homes, businesses and streets located on the backshore. Damage was particularly severe to foreshore stone, brick or concrete walls, which were undercut. Satellite images showed a low pressure system centered in the Pacific Ocean just north of the entrance to the Gulf of Fonseca, around which circulating winds directed waves into the Gulf’s narrow mouth. The Consigüina Peninsula and several extinct or dormant volcanic islands protect most of the Gulf of Fonseca from ocean waves. Most of the protected shoreline consists of mangroves along drowned river mouths. The only extensive sand beach stretches north and south from Cedeño, where ocean waves have a direct path to land through the mouth of the Gulf of Fonseca. Longshore transport away from Cedeño in both directions has created spits on the north and south ends of the beach. The beach at Cedeño is higher, with more sand accumulated along the backshore than elsewhere. We think that the very process responsible for destroying structures on this beach in September 2002 is also the reason that this sand beach exists. Direct wave attack winnows or removes silt and clay that otherwise accumulate along protected shorelines in the Gulf. Floodplains bordering rivers that drained through the Gulf of Fonseca during low Pleistocene sea levels probably resembled the sandy floodplain and delta of the nearby modern Choluteca river. These deposits are a ready supply of sand for reworking and transport by waves to the form the narrow barrier island. COPECO has declared the foreshore a zone of risk and recommends that it remain free of structures. The mayor of Cedeño has arranged to relocate former shoreline residents and plans to restore the beach to its natural state as an asset to attract tourism.