Monitoring of the 1985/86 Beach Nourishment Project at Bar Beach, Victoria Island, Lagos, Nigeria

Ibe, A. C.; Awosika, L. F.; Ibe, C. E.; Inegbedion, L. E.; ,

Monitoring of the 1985/86 Beach Nourishment Project at Bar Beach, Victoria Island, Lagos, Nigeria

by A. C. Ibe, Nigerian Inst for Oceanography and, Marine Research, Lagos, Nigeria,
L. F. Awosika, Nigerian Inst for Oceanography and, Marine Research, Lagos, Nigeria,
C. E. Ibe, Nigerian Inst for Oceanography and, Marine Research, Lagos, Nigeria,
L. E. Inegbedion, Nigerian Inst for Oceanography and, Marine Research, Lagos, Nigeria,

Document Type: Proceeding Paper

Part of: Coastal Zone '91

Abstract:

Bar Beach, Victoria Island, is Nigeria's foremost leisure beach and has been the site of very active erosion following the completion in 1912 of two stone breakwaters perpendicular to the shore to protect the dredged entrance into Lagos harbor. The situation became so grave that in 1958 a groin was constructed at the foot of the eastern breakwater to avoid the undermining of the breakwater by erosion. Since then, one form of artificial sand nourishment or another has been implemented to stem the retreat with progressively shorter intervening periods. Rates of shoreline retreat reached 25-30 m annually in the period after the 1981 beach replenishment. Following the beach nourishment in 1985/86 that put about 3 million cubic meters of sand on the beach, the authors established 11 stations on the beach for beach profiling and process measurements to determine littoral processes and identify sediment sources and sinks. Erosion was a continuous process over the study period, averaging between 46 and 110 m at various points between June 1986 and August 1989 with the more pronounced erosion occurring in the immediate post-replenishment period. A more detailed analysis indicated a seasonal variation in the cycle of erosion. Steep surf zone profiles with average gradients 1:66 to 1:21 were recorded within 100 m from the shoreline at all stations. A review of possible erosion control measures for Bar Beach reveals that periodic sand nourishment with adequate criteria remains the most credible and cost-effective option.

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