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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 watershed‐scale 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 cross‐scale 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⁻² yr⁻¹; average of 1.4 (0.2–6.5) g phosphorus m⁻² yr⁻¹), the range in deposition rates locally across a floodplain was greater (average of 4.6 (0.06–21.7) kg sediment m⁻² yr⁻¹; average of 6.4 (0.1–41.1) g phosphorus m⁻² yr⁻¹). Local variables that described the proximity to water and sediment sources, and frequency with which the plot was activated by a flood, had the greatest relative contribution to boosted regression tree models of phosphorus deposition rates, highlighting the importance of river–floodplain connectivity for floodplain functioning and the profound impact of human activities that limit such connectivity. Patterns identified in our study may guide prioritization of restoration and conservation practices designed to capture sediment and phosphorus on floodplains.

A paired‐catchment study began in 2000 to assess the hydrologic effects of high‐elevation development on Mt. Mansfield, Vermont's highest summit (1340 m). West Branch Little River drains 12.08 km²and encompasses a large ski resort. Adjacent Ranch Brook drains 9.83 km²of minimally disturbed second‐growth forest. The two catchments have similar elevation, aspect, surficial and bedrock geology, and vegetation. The resort was well established before this study, but it underwent a major expansion during the period 2004–2008. The expansion included new ski lifts and trails, a large hotel, roads and second home development, a 435 000‐m³snowmaking storage pond and a nine‐hole golf course, increasing the extent of cleared/open land from 17% to 24%. Runoff from the developed West Branch Little River catchment was 21% greater than Ranch Brook over the duration of the study, but varied widely each year from 10% to 42%. This high variability occurs both on the interannual and individual storm scales, and is consistent with expectations from future climate projections. Hydrologic variability is on the rise, as shown by an increase in stream flashiness in both catchments over the 20 years of our study. Resort expansion, which provided for stormwater management, had no discernible effect on the overall runoff difference nor the flow distribution at the scale of the catchments, but sedimentation, water quality impacts and localized erosion cannot be ruled out. Forest clearing, impervious and hardened surfaces, and skier‐compacted and machine‐made snow may all cause enhanced runoff. However, the greater runoff at West Branch, which occurs primarily during snowmelt and summer, may arise partly from greater precipitation capture in the complex mountain topography. Development pressure on the mountain landscape continues to mount, but managers may also need to consider the confounding effects of a changing climate.

Excessive phosphorus (P) export to aquatic ecosystems can lead to impaired water quality. There is a growing interest among watershed managers in using restored wetlands to retain P from agricultural landscapes and improve water quality. We develop a novel framework for prioritizing wetland restoration at a regional scale. The framework uses an ecosystem service model and an optimization algorithm that maximizes P reduction for given levels of restoration cost. Applying our framework in the Lake Champlain Basin, we find that wetland restoration can reduce P export by 2.6% for a budget of $50 M and 5.1% for a budget of $200 M. Sensitivity analysis shows that using finer spatial resolution data for P sources results in twice the P reduction benefits at a similar cost by capturing hot-spots on the landscape. We identify 890 wetlands that occur in more than 75% of all optimal scenarios and represent priorities for restoration. Most of these wetlands are smaller than 7 ha with contributing area less than 100 ha and are located within 200 m of streams. Our approach provides a simple yet robust tool for targeting restoration efforts at regional scales and is readily adaptable to other restoration strategies.

The combined impacts of climate change and ecological degradation are expected to worsen inequality within society. These dynamics are exemplified by increases in flood risk globally. In general, low‐income and socially vulnerable populations disproportionately bear the cost of flood damages. Climate change is expected to increase the number of people exposed to fluvial flood risk and cause greater property damages. Floodplain restoration has the potential to mitigate these impacts, but the distribution of future risks among different types of property owners under these altered conditions is often unknown.

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Land use can significantly alter soil P forms, which will influence P loss in runoff. Organic P (P_o) compounds are an important component of soil P, but their forms and cycling in soils with different land uses are still poorly understood. In addition, streambanks are potential sources of P loss; P forms and concentrations in streambank soils may vary with land use, affecting potential P loss to water. This study used solution³¹P nuclear magnetic resonance spectroscopy to characterize and quantify P in interior and streambank soils (0–10 cm) under duplicate sites from four different land uses along streams in the Missisquoi River basin (VT, USA): silage corn, hay meadow, emergent wetlands, and forest. Orthophosphate monoesters were the dominant P compound class regardless of land use or landscape position. Forest soils had the lowest P_oconcentrations, less labile P forms than other soils, and significantly lower concentrations of total inositol hexakisphosphates and total orthophosphate monoesters compared with corn soils. Riparian buffer zones for agricultural soils lowered P concentrations in streambank soils for many soil P pools relative to interior soils. The wetland soils of this study had P concentrations and P forms that were similar to those for interior agricultural soils and generally showed no reduction in P concentrations in streambank soils relative to interior soils. This is consistent with the role of wetlands as P sinks in the landscape but also suggests these wetlands should be carefully monitored to minimize P accumulation, especially in streambank soils.