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Abstract The elevation of natural river levees can vary considerably along the length of a river, and low‐lying features such as secondary floodplain channels allow for hydrologic exchange between a river and its floodplain over a range of discharges. This hydrologic, “river‐floodplain connectivity” plays a role in attenuating flood waves and transporting fluvial material to floodplain ecosystems. However, flood wave attenuation and transport are also limited by the available storage provided by floodplains. In this study, we explore the combined controls of river‐floodplain connectivity and floodplain width on flood wave attenuation and transport, and how those controls change as flood magnitude increases. We develop idealized river‐floodplain models based on the geometry of the lower Trinity River in Texas, USA, varying floodplain width, peak discharge, and degree of river‐floodplain connectivity, which we prescribe by varying the width of a secondary channel connecting the river to the floodplain. We show that attenuation transitions from connectivity‐limited to storage‐limited as discharge increases. Secondary channel conveyance allows for floodplain inundation at lower discharges, but also fills the floodplain faster and, for larger floods, can cause higher flood peaks downstream. Greater secondary channel conveyance and wider floodplains increase fluxes to the floodplain, but secondary conveyance allows the floodplain to drain faster while wider floodplains have longer average residence times. This study presents a framework for understanding how secondary channel conveyance and floodplain width combine to modulate lateral flow exchange, residence times, and flood wave attenuation, and can guide successful management of river systems and future restoration efforts.
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This content will become publicly available on April 11, 2026
Scaling laws for sediment storage and turnover in river floodplains
Nearly 10% of Earth’s continents are covered by river floodplains. These landscapes serve as weathering reactors whereby particles eroded from mountains undergo chemical and physical alteration before being exported to oceans. The time a particle spends in floodplain reservoirs regulates the style and extent of continental chemical weathering and the fate of terrestrial organic carbon. Despite its importance for the global carbon cycle, we still lack a quantitative understanding of floodplain storage timescales. Using a combination of geomorphic mapping, radiocarbon and luminescence dating, and numerical simulations of meander dynamics, we identify well-conserved scaling laws that describe floodplain storage times. Our results reveal that, to first order, floodplain storage durations are set by the ratio of river width to migration rate. The fact that most rivers erode about 1% of their width per year leads to a typical floodplain storage duration of ~5 thousand years.
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- PAR ID:
- 10658780
- Publisher / Repository:
- Science Advances
- Date Published:
- Journal Name:
- Science Advances
- Volume:
- 11
- Issue:
- 15
- ISSN:
- 2375-2548
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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