ABSTRACT

Texas A&M University-Corpus Christi is sponsoring a study on the feasibility of a recreational beach for its campus located on Ward Island. The beach would front the northern shoreline of Ward Island along Corpus Christi Bay, Corpus Christi, Texas. The functional design process provided an opportunity to investigate the nearshore morphology and sediment characteristics of this unstudied shore.

Seasonal profile surveys were conducted from the spring of 1994 to the winter of 1996 and included sediment sampling along select transects. Repetitive profile surveys taken along the same transect proved average survey elevation accuracy to be better than 0.7 cm. The surveys extended the entire 2.6 km length of the northern Ward Island shoreline from the Oso Inlet to the Blind Oso Inlet. An unusually flat and wide nearshore region was identified. The shallow (1.1 m) nearshore typically extends 150-200 m offshore. The depth of closure, or active region of sediment transport, is at 1.6 m Mean Tide Level, as identified through profile surveys. The sediment in the nearshore is moderately sorted, inclusive graphic standard deviation of 0.02 mm, fine sand with a median grain size diameter of 0.14 mm.

The survey defined a well-developed longshore bar system that was previously observed visually during periods of low tide and in aerial photographs. This system consists of four to seven sandbars that slowly migrated offshore during the study period, independent of season. Inspection of aerial photographs taken from 1934 to 1996 indicate that the number and linearity of longshore bars has decreased. In addition, the bars west of the Blind Oso Inlet appear to be superimposed on a raised subsurface feature. This plateau was also identified at Poenisch Park, located west of Ward Island, indicating that the sandy nearshore region is a veneer over a firm relic shelf. This study hypothesizes that the decrease in number and linearity of the longshore bar system is related to a decrease in sand resources. Thus, natural accretion of a beach along Ward Island is unlikely. Therefore sandy-fill material along with coastal structures will be necessary to provide a stable beach in this region.