Channel-floodplain connectivity within a coastal riverine landscape of Texas

Authors: Cesar Castillo*, Texas A&M University, Inci G├╝neralp, Texas A&M University, Billy Hales, Texas A&M University
Topics: Geomorphology, Water Resources and Hydrology, Environmental Science
Keywords: geomorphology, surface water hydrology, landscape ecology, flooding, graph theory
Session Type: Paper
Day: 4/6/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: Hoover, Marriott, Mezzanine Level
Presentation File: No File Uploaded

Analyzing surface water connections between the main channel and floodplain of a meandering alluvial river is an emerging research topic and it has many implications with regard to environmental flows. In this study, we examine the spatial relationship between channel-floodplain connectivity and river stage (stage, herein) within the coastal channel-floodplain system of Mission River on the Coastal Bend of Texas. Utilizing a two-dimensional hydrodynamic model, we determine the spatial characteristics of surface water inundation under various stages and their associated expansion processes as predicted by the flood pulse concept. We also analyze the role that surface water inundation plays in establishing connectivity within the riverine landscape by disaggregating the landscape into habitat patches. We quantify channel-floodplain and between-patch connectivity induced by surface water connections at our modeled stages using graph theory. Our results indicate that landscape-level connectivity and associated system attributes (complexity and synchronization) change nonlinearly with increases in stage. The greatest increases in landscape-level connectivity occurs below published bankfull conditions (bankfull stage is ~8 m). Our analysis also reveals that landscape connectivity induced by surface water connection exhibits a hub-like spatial structure that is driven by low spots within the floodplain and small channels that provide connection to the main channel. The framework we present in this study allows for a detailed characterization of channel-floodplain and landscape connectivity that can be used to identify the most critical locations and fluvial conditions for a river reach that coincide with the management/restoration goals for lowland riverine environments.

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