LATERAL MOVEMENT ALONG THE RED RIVER, TX-OK BORDER: THE VARIABILITY OF RIVER BEHAVIOR ACROSS ENVIRONMENTAL GRADIENTS

The Red River has historically demonstrated a propensity for lateral channel movement along the TX-OK border, periodically adjusting both the macrochannel banks and the alignment of the inset channel. Given that the border is defined by the ‘southern vegetated bank’, this lateral movement can alter the physical location of a political boundary. Therefore, it is important to establish a set of expectations regarding the potential variability in the capacity for lateral movement along the Red River. We compiled sequential sets of aerial imagery for four years (1996, 2004, 2010, 2016) in each of the 11 Texas counties whose northern border with Oklahoma is defined by the Red River. Using ArcGIS, we defined the banks and centerline of the most recently active channel margin for each county and year, and quantified the lateral movement for each time span (1996-2004, 2004-2010, 2010-2016) at 50 m intervals along the channel. We find that the capacity for lateral movement varies downstream along the Red River, with peak average movement occurring in three upstream counties (Wilbarger, Wichita, Clay Co.), while the highest single movement occurred downstream (Bowie Co.), resulting from a meander bend cutoff. The amount and variability of lateral channel movement is a reflection of the complex interplay between external (e.g. climate, lithology, valley confinement) and internal (e.g. sediment connectivity, discharge regime, channel pattern) factors. As each of these factors vary downstream, so too does the capacity for lateral channel adjustment. We further aim to relate our observed pattern of lateral movement to environmental gradients of change in both external and internal controlling factors to explicate the Red River’s capacity for lateral movement and to define the channel behavior.