114-1 Modern Water and Sediment Transport Patterns in Alluvial Ridge Basins of the Rio Grande Delta, TX

Session: Geomorphology and Surface Processes Across the Solar System (Poster)

Poster Booth No.: 294

Presenting Author:

Waqid Nabi

Authors:

Nabi, Waqid¹, Dong, Tian Yang², Rutan, Kynan³, Benavides, Jude A.⁴, Kim, Jongsun⁵, Gonzalez, Juan Luis⁶, Carlson, Brandee⁷

(1) University of Texas Rio Grande Valley, Edinburg, TX, USA, (2) University of Texas Rio Grande Valley, Edinburg, TX, USA, (3) University of Texas Rio Grande Valley, Edinburg, Texas, USA, (4) University of Texas Rio Grande Valley, Edinburg, Texas, USA, (5) University of Texas Rio Grande Valley, Edinburg, Texas, USA, (6) University of Texas Rio Grande Valley, Edinburg, TX, USA, (7) University of Houston, Houston, TX, USA,

Abstract:

River deltas contain nutrient-rich (e.g., nitrogen) land and dynamic ecosystems, supporting economic growth, biodiversity in wetlands, and agricultural activities. Deltas build land via channel avulsions, which often contain multiple generations of abandoned channels with high levees in the coastal plain. Alluvial ridge (AR) basins thus can form between the high levees as shallow-tide-influenced depressions and occupy a significant portion of the broader delta. The fluid flow, sediment transport, and depositional patterns in these AR basins are poorly understood, which hinders the development of a comprehensive theory of deltaic land building. Hence, a field study is conducted in the Bahia Grande (BG) Complex, an AR basin system bounded by several abandoned channels (regionally known as Resacas) of the Rio Grande Delta (RGD). Specifically, tilt current meters, water level data, and turbidity loggers are deployed to measure water depth, flow velocity and direction, and suspended sediment concentration. Water and surface sediment samples are also collected to estimate the distribution of suspended and bed sediment concentrations in the AR basin. Preliminary results indicate enhanced flood tide and attenuated ebb tide velocities during summer, whereas fall is characterized by intensified ebb tide and comparatively reduced flood tide velocities. This pattern can be attributed to the basin configuration, featuring a southeast-oriented inflow channel further modulated by prevailing southeasterly winds, influencing tidal velocity asymmetries. Meanwhile, the storm periods exhibit symmetrical tidal activity, with similar flood and ebb tide velocities. These AR basins are likely to be net depositional due to the dominant flow velocities and duration of flood tide flow. These findings elucidate the impact of seasonal variability in sedimentation in non-channelized river delta areas, thereby contributing to the advancement of theories on deltaic land building.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7691

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