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Reach‐scale changes in channel geometry and dynamics due to the coastal backwater effect: the lower Trinity River, Texas
Author(s) -
Smith Virginia,
Mason Jasmine,
Mohrig David
Publication year - 2019
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.4754
Subject(s) - geology , hydraulics , point bar , channel (broadcasting) , sediment transport , geometry , geomorphology , open channel flow , flow (mathematics) , elevation (ballistics) , hydrology (agriculture) , sediment , geotechnical engineering , fluvial , structural basin , physics , mathematics , engineering , electrical engineering , thermodynamics
Abstract In this paper we use multiple field surveys spanning several decades to systematically evaluate the geomorphic consequences of a change in flow hydraulics from uniform flow to backwater flow for the lower Trinity River in east Texas, USA. Spatial changes in lateral migration rate, channel geometry, and point bar size correspond to two distinct geomorphic zones. Within the upstream uniform flow reach, the river channel is defined by fully developed point bars and a high rate of lateral channel migration. This zone transitions where the median channel bottom elevation drops below sea level. At this point flow is affected by the backwater influence of the Trinity Bay water surface elevation, as opposed to being bed slope control dominated. The change in hydraulics within the backwater zone is reflected in the channel morphology, which is characterized by smaller point bars, narrower and more symmetrical cross‐sectional channel geometry, lower channel migration rates, and little to no bend deformation or cutoffs. Studying the connection between channel geometry, river bend kinematics, sediment transport, and fluid mechanics in each zone provides a deeper understanding of the relationship between channel shape and river mechanics. © 2019 John Wiley & Sons, Ltd.