A new longitudinal approach to assess hydrologic connectivity: Embanked floodplain inundation along the lower Mississippi River

Abstract

Abstract:Hydrologic connectivity is fundamental to understanding floodplain processes along meandering river corridors. This study contributes to understanding hydrologic connectivity by utilizing a high resolution Light Detection and Ranging DEM with a new GIS-based approach for identifying the precise elevation of flood stage. The method created a high-resolution longitudinal channel bank profile, enabling a detailed examination of embanked floodplain hydrologic connectivity. A simple channel crosssection approach is likely to result in a large underestimation of floodplain inundation and hydrologic connectivity along meandering river floodplains because of differences in the elevation of the natural levee surface relative to floodplain bottoms and the considerable variability in the elevation of the channel bank profile. There is a large disparity in discharge duration associated with floodplain inundation in comparison to river channel bank inundation. A discharge duration of 10% is associated with inundation of 87% of the floodplain surface whereas only 53% of the channel bank profile is overtopped. An apparent threshold in inundation occurs as the discharge duration decreases below about 35%. While a duration of 25% results in very little of the channel bank being overtopped, it inundates 50% of the floodplain surface. Floodplain borrow pits, which are created in association with dike construction, represent a constant anthropogenic influence on the lower Mississippi embanked floodplain morphology, and are inundated by low discharge magnitudes. The results of the investigation shed new light on the topic of hydrologic connectivity for an important embanked fluvial system that has previously received little attention concerning its physical floodplain processes.

Flooding and Surface Connectivity of Taxodium‐Nyssa Stands in a Southern Floodplain Forest Ecosystem

“…However, the 1D approach lacks the functionality for modelling complex, dynamic overland flow processes associated with the more frequent seasonal floods that are central in initiating floodplain connectivity during lower discharge flows (cf. Hudson et al, 2013). In contrast, TUFLOW explicitly models flow movement through multiple, intricately-connected overland flow pathways (Horritt and Bates, 2002), which is critical for capturing distributary and backwater flood pulses that occur with greater frequency.…”

Seasonal Water Exchanges between China’s Poyang Lake and Its Saucer-Shaped Depressions on River Deltas

“…Moreover, in shallow lake-wetlands, the rate, duration and magnitude of water exchange between depressions and the adjacent main lake also have major influences on the water quality, aquatic habitat, organic matter and organisms, since movement of chemical constituents and biota are often associated with water flow [11][12][13]. Therefore, hydrological connectivity and water exchange are especially important considerations for shallow lake-wetlands [14,15]. A better understanding of these hydrologic processes is critical to helping regulate wetland structure and assess the status of vulnerable delta systems [1,16,17].…”

Spillage sedimentation on large river floodplains

“…Chen et al (2011) reported 313 historically recorded breaches in artificially raised levees on the superelevated Yellow River in a 300 year period. Waters and sediment may spread via low bank points without main channel banks being fully overtopped except in the most extreme events (Hudson et al, 2013). Tributary channels may also significantly spread main channel sediment through the reversed flows that back up them from main rivers (Day et al, 2008).…”