Quantifying river-floodplain connectivity of the Lower Rio Grande
Creators: name: Davila, Sara Esther
name: 0000-0001-9539-6500
Publisher: name: The University of Texas at Austin
Year: 2022
Subjects: River-floodplain connectivity
Hydrodynamic modeling
Residence times
Lateral exchange
Lower Rio Grande

description: Hydrological connectivity is the movement of energy and matter between channels to an adjacent floodplain. When there is a hydrological connection between river and floodplain, it is classified as river-floodplain connectivity. Characterizing river-floodplain connectivity can provide useful information for land and flood management, as well as ecological enhancement. The Lower Rio Grande River is controlled by anthropogenic features designed for energy generation, agricultural production, and water diversion for regions like the Rio Grande Valley (RGV), Texas, USA, and the state of Tamaulipas in Mexico. An increase in flood events along the RGV would cause concern over the riverine interactions with the adjacent floodplains during periods of high discharges and/or rainfall. Numerical models can help in this regard by characterizing river-floodplain systems but are often limited by the scarcity of high-resolution topographic data for flat, low-sloped regions like the Lower Rio Grande area. This limitation of data has hindered the development of accurate numerical models of the Lower Rio Grande region as the dynamic nature of extreme weather requires periodic model updates with the most recent topographic, hydrologic, and hydraulic conditions of the Lower Rio Grande region. To improve understanding of river-floodplain connectivity in the Lower Rio Grande River region, this study uses a finite-volume, 2D hydrodynamic model with 1-meter high resolution lidar topographic data to better model river-floodplain connectivity in the Lower Rio Grande in correspondence of discharges over a range of return periods. The numerical model is calibrated and validated using historical data collected at a nearby gage station, and metrics are used to quantify river-floodplain connectivity in the Lower Rio Grande. In particular, we aim to identify what locations along the study domain get inundated during different return period events, and quantify the water depths, residence times, and lateral exchange that are associated with the inundation patterns. These quantification metrics allow us to holistically account for the surface water hydrologic connectivity of the floodplain and determine locations along the domain that experience the most connectivity. We found that high vegetative areas and levees influence river-floodplain interaction by acting as buffers along the floodplain. Oxbow lakes and levees systems are also shown to be inundated in 50% of the return periods analyzed. Additionally, we found that residence times are highest at lower return periods, while lateral exchange are highest at high return periods. This inverse behavior indicates that water can ultimately be transported further into the floodplain during larger storm events, while the lower storms can cause the floodplain to experience longer water retention in the floodplain. With some further improvements, these data can be leveraged to inform local stakeholders about the river interaction with the floodplain and integrated in decision-making tools to ultimately develop management strategies that make river systems more resilient to future climate scenarios.