Colin Reginald Thorne

Floodplain disconnection caused by channel incision and/or levee construction has led to widespread loss of riparian habitats and ecosystem functions globally. Restoring full stream–floodplain connectivity is increasingly promoted, yet evidence of ecological outcomes remains limited. This study evaluates the initial performance of two Stage 0 restoration projects on Whychus Creek, Oregon, which reconnected incised channels to their historical floodplains in 2012 and 2016. We combined pre- and post-restoration vegetation surveys along fixed transects with hydrogeomorphic-based riparian and wetland function assessments and applied quantitative analyses, including Kruskal–Wallis tests, Jaccard correlations, Sorensen similarity indices, and factor analysis, to compare changes in plant assemblages and ecosystem functions across restored, transitional, and unrestored reaches. Our research results indicate that two years post-restoration, the active riparian area expanded 2.5-fold, species richness and structural diversity increased significantly, and riparian and wetland functions such as water storage, sediment retention, and habitat support for fish and amphibians improved markedly. Numbers of anadromous salmonids also increased markedly. This is important as salmon recovery is a regional stream restoration goal. Comparisons with a reach restored six years earlier suggest a positive trajectory toward mature, resilient ecosystems. These findings demonstrate that Stage 0 restoration can rapidly reestablish complex habitat mosaics and enhance ecosystem services critical for biodiversity, water quality, and flood resilience. Practically, this evidence supports process-based restoration strategies that prioritize full floodplain reconnection as a cost-effective approach to reversing long-term ecological degradation. Continued monitoring is essential to guide adaptive management and strengthen the evidence base for the wide-scale implementation of valley-floor wide stream restoration.

Floodplain disconnection caused by anthropogenically-triggered channel incision or artificial levee construction, has led to widespread loss of riparian habitat and ecosys-tem functions in river systems across the globe. Restoring connectivity is now consid-ered essential to recover lost biodiversity and improve water quality, yet evidence for the ecological outcomes of full reconnection remains limited. This study evaluates the ecological effectiveness of two Stage 0 restoration projects on Whychus Creek, Oregon, which reestablished stream–floodplain connectivity across the entire valley floor in 2012 and 2016, respectively. We used pre- and post-restoration vegetation surveys along fixed transects to assess changes in plant assemblages and compared these with an unre-stored reach and a reach restored six years earlier. Two years after the restoration was carried out, the active riparian area had expanded 2.5-fold and supported a patchy, shifting mosaic of aquatic, wetland, riparian, mesic, and upland habitats. Species rich-ness and structural diversity increased significantly. We also saw found improvements in key wetland functions such as water storage, sediment retention and nutrient cycling – evidence of healthy, heterogenous habitats that can support a wide range of species. Our results show that Stage 0 restoration can rapidly reestablish complex habitat net-works and deliver diverse ecological benefits. Continued monitoring is essential to as-sess the long-term trajectories of post-restoration succession and resilience. This study contributes to the growing evidence base for process-based restoration that pri-oritizes full floodplain reconnection in anthropogenically-incised rivers.

Lateral connectivity between rivers and terrestrial landscapes is critical for both river and landscape health. Due to widespread anthropogenic degradation of riverscapes, river management is aiming to connect rivers to floodplains, riparian zones, and wetlands, putting a spotlight on lateral connectivity. However, there is currently no consensus on how to conceptualize and study lateral connectivity in rivers across disciplines. Here, we review lateral connectivity between riverscapes and terrestrial landscapes. We focus on the natural sciences, considering hydrology, geomorphology, ecology and biogeochemistry, but also consider social connectivity and the management and restoration of lateral connectivity. We emphasize the importance of considering the bidirectional nature of lateral connectivity, operating both into and out of river channels and the balance between these directions. The resulting “lateral connectivity balance” provides a framework to understand natural spatial and temporal variability in connectivity. Anthropogenic impacts have swung the balance of lateral connectivity, enhancing the transport of materials into and through river networks while suppressing fluxes from rivers to adjacent landscapes. We conclude that further research at the interfaces between the aquatic and terrestrial components of riverscapes is critical to advance our conceptual understanding of river and catchment systems. We propose that such research should be framed within the paradigm of “rebalancing” lateral connectivity, explicitly recognizing the natural bidirectionality of laterally connecting processes, the significance of the hydrologic, geomorphic, and biologic functions they support, and the value to society of the ecosystem services and climate change resilience they provide.

Blue-Green Cities manage flood risk by recreating more naturally oriented water cycles in urban areas through the restoration of natural drainage channels, reduction in impervious surfaces and implementation of Blue-Green Infrastructure (BGI - for example, swales, wetlands, green roofs) to enhance infiltration, attenuation and surface storage of water. Blue-Green Cities work synergistically to mimic predevelopment hydrology while generating multiple co-benefits to the environment, society and economy. The chapter expands on the Blue-Green City concept, providing an overview of existing research in this field. International examples show how the barriers hindering progression towards Blue-Green Cities are being overcome. Emerging research into adaptation pathways, natural capital accounting and social practice approaches for understanding community preferences demonstrate how research into Blue-Green Cities is moving beyond hydrodynamic modelling to consider decision-making under future uncertainty, the inclusion of environment and social benefits in business cases and the pivotal role of community preferences in designing blue-green systems.

A maturing body of evidence suggests that anthropogenic impacts on river‐wetland corridors (RWCs) are greater and more widespread than previously recognized. Partly, this stems from the difficulty of differentiating between legacy anthropogenic impacts and channel evolution resulting from natural disturbances. Here, we apply the geomorphic grade line (GGL) relative elevation model (REM) method to reveal pre‐Anthropocene fluvial features for a 42‐km reach of Entiatqua (English translation—the Entiat River) in the North Cascade Mountains, USA. We began by long profiling the entire length of the river valley and defining distinct valley segments based on breaks in profile. Next, we developed models of the valley profile for each segment, known as GGLs, and used them to develop high‐resolution REMs by detrending LiDAR‐derived digital elevation models. We then used the GGL‐REMs to map relict fluvial features in the valley floor. Validating the GGL‐REMs using surficial geologic maps, ¹⁴Cdated soil profiles, and the identifiable remnants of historic dams allows us to differentiate surfaces associated with the pre‐Anthropocene from those resulting from anthropogenic activities, including splash damming, channel straightening, large wood removal, and beaver extirpation. Our findings reveal 1–2.5 m of anthropogenically‐driven channel incision in unconfined and partially‐confined valley segments, wherein fluvial sediment balances transitioned from being net depositional to erosive, and later neutral, with river environments in these segments shifting from being complex, ecologically‐rich, RWCs to simpler, ecologically‐impoverished, single‐thread channels, like those found in confined valley segments. The adverse impacts of post‐Anthropocene fluvial responses on salmon habitats were likely profound and may help explain historical and ongoing declines in populations of listed species, including Chinook Salmon (Oncorhynchus tshawytscha) and Steelhead Trout (Oncorhynchus mykiss). Our study of Entiatqua, together with evidence from other western US rivers, demonstrates that the GGL‐REM approach can be used to re‐envisage pre‐Anthropocene fluvial process‐form domains including identifying valley segments wherein fluvial responses to human development have disconnected RWCs. Once the pre‐Anthropogenic conditions of rivers like Entiatqua have been recognized, the case for restoring lost RWCs to unlock their ecological potential becomes compelling.

Background: Historically, wildfire regimes produced important landscape‐scale disturbances in many regions globally. The “pyrodiversity begets biodiversity” hypothesis suggests that wildfires that generate temporally and spatially heterogeneous mosaics of wildfire severity and post‐burn recovery enhance biodiversity at landscape scales. However, river management has often led to channel incision that disconnects rivers from their floodplains, desiccating floodplain habitats and depleting groundwater. In conjunction with predicted increases in frequency, intensity and extent of wildfires under climate change, this increases the likelihood of deep, uniform burns that reduce biodiversity.Predicted synergy of river restoration and biodiversity increase: Recent focus on floodplain re‐wetting and restoration of successional floodplain habitat mosaics, developed for river management and flood prevention, could reduce wildfire intensity in restored floodplains and make the burns less uniform, increasing climate‐change resilience; an important synergy. According to theory, this would also enhance biodiversity. However, this possibility is yet to be tested empirically. We suggest potential research avenues.Illustration and future directions: We illustrate the interaction between wildfire and river restoration using a restoration project in Oregon, USA. A project to reconnect the South Fork McKenzie River and its floodplain suffered a major burn (“Holiday Farm” wildfire, 2020), offering a rare opportunity to study the interaction between this type of river restoration and wildfire; specifically, the predicted increases in pyrodiversity and biodiversity. Given the importance of river and wetland ecosystems for biodiversity globally, a research priority should be to increase our understanding of potential mechanisms for a “triple win” of flood reduction, wildfire alleviation and biodiversity promotion.