Multi‐scale drivers of spatial patterns in floodplain sediment and phosphorus deposition

Abstract

The capacity for floodplains to capture sediment and filter pollutants is spatially variable and depends on the complex interactions of geomorphic, geologic, and hydrologic variables that operate at multiple scales. In this study, we integrated watershedscale and local assessments to improve our understanding of floodplain depositional patterns. We developed a dataset of event-scale observations of sediment and phosphorus deposition rates distributed at 129 plots across large environmental gradients of floodplain topography, valley geometry, and watershed characteristics in the Lake Champlain Basin, Vermont. Plot-scale observations were used to evaluate the crossscale influence of environmental factors and were summarized into site-scale averages to explore regional trends. Consistent with other studies, floodplain deposition generally scaled with drainage area, but trends were longitudinally discontinuous and depended on variations in valley width and slope. While variability in deposition patterns at the watershed-scale was large (average of 2.0 (0.2-9.8) kg sediment m À2 yr À1 ; average of 1.4 (0.2-6.5) g phosphorus m À2 yr À1 ), the range in deposition rates locally across a floodplain was greater (average of 4.6 (0.06-21.7) kg sediment

Terrain‐derived measures for basin conservation and restoration planning

“…However, this pattern was associated with substantial lateral/vertical disconnection between channel and floodplain, as signified by ER <3. Floodplains that experience gradual spillover at smaller First Spillover Design Floods have a more frequent exchange of water and sediment between the channel and floodplain, all of which are needed to support healthy ecosystem function (Diehl et al, 2023; Opperman et al, 2010; Tockner & Stanford, 2002; Ward, 1989; Ward & Stanford, 1995). Conversely, reaches with substantial disconnected floodplain areas are likely to have degraded floodplain function.…”

“…The intermediate alluvial or mixed reaches (identified along the bottom of Figure 8) are then influenced by ‘flux controls’ (Khan et al, 2021), including tributary junctions that deliver water and sediment on variable timings and development‐related disturbances including removal of vegetation, encroachment of built infrastructure, and channel modifications (e.g., straightening, berming). These flux controls interact in nonlinear and complex ways to influence channel and floodplain morphology, which can in turn influence conveyance of floodwaters and sediment (Diehl et al, 2023; Macnab et al, 2006).…”

“…The above photographs were chosen to best illustrate the restoration or conservation concepts and do not necessarily reflect the actual study reach. [Color figure can be viewed at wileyonlinelibrary.com] between the channel and floodplain, all of which are needed to support healthy ecosystem function (Diehl et al, 2023;Opperman et al, 2010;Tockner & Stanford, 2002;Ward, 1989;Ward & Stanford, 1995). Conversely, reaches with substantial disconnected floodplain areas are likely to have degraded floodplain function.…”

Modeling Phosphorus Retention and Release in Riparian Wetlands Restored on Historically Farmed Land

“…Our study areas were on the lower end of energy settings within the VT-LCB (Fig. 2a) (Diehl et al 2022). So, it is not surprising that the particulate P deposition at the 3 sites that we monitored was on the lower end (up to approximately 1 g P m -2 yr -1 ) of the spectrum reported by Diehl et al (2022) for a broader suite of floodplains in the VT-LCB (1 g P m -2 yr -1 to >100 g P m -2 yr -1 ).…”

Runoff of Water and Its Quality under the Combined Impact of Agricultural Activities and Urban Development in a Small River Basin

“…The thus-far-accumulated experience in the study and assessment of sedimentation in the floodplains of rivers in Western Europe [24][25][26], Ukraine [27][28][29][30], Russia [31][32][33][34], Asia [35,36], the USA [37,38], and Australia [39] presents a considerable range of methods and technologies. In addition, the effectiveness of the concept of a joint erosionsedimentation process [40]-according to which the entire set of watercourses, from temporary slope watercourses to large rivers, is an interconnected system-is gaining increasing recognition.…”