Character and Growth of Deltaic Deposits in Lewisville Lake, Texas

During the last 60 years, a large delta has been built into Lewisville Lake reservoir by the Elm Fork of the Trinity River. Such deltas contribute significantly to reservoir sedimentation and may represent important accumulation sites for sediment-bound nutrients and contaminants. This study was designed to provide details of the rate of growth, structure, and textural composition of the Elm Fork delta. The progradation rate of the delta was determined on the basis of sequential aerial photographs. Information on its structure and composition was obtained from depthsounder profiles, sampling of surficial sediments, and coring of subsurface deposits. Progradation of the delta was found to be markedly uneven, both over time and across the width of the reservoir. The delta exhibits a number of common deltaic characteristics, including pronounced levees along the main distributary channel and a distinctive foreslope. Sand-sized sediment appears to be confined mainly to the immediate vicinity of the main distributary channel, which may reflect channeling of the flow by the levees