Ecologically relevant geomorphic attributes of streams are impaired by even low levels of watershed effective imperviousness

Vietz, Geoff; Sammonds, Michael J.; Walsh, Christopher J.; Fletcher, Tim D.; Rutherfurd, Ian; Stewardson, Michael J.

doi:10.1016/j.geomorph.2013.09.019

Cited by 98 publications

(92 citation statements)

References 63 publications

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“…We found that hydrologic alteration generally occurred in catchments with greater than 5% total impervious cover (with most alteration occurring above 2% total imperviousness), which is similar to other studies that have shown that channel degradation to due to hydromodification occurs at relatively low levels of imperviousness (Hawley and Bledsoe, 2011;Hawley, Bledsoe, Stein, & Haines, 2012;Vietz et al, 2016). We found that hydrologic alteration generally occurred in catchments with greater than 5% total impervious cover (with most alteration occurring above 2% total imperviousness), which is similar to other studies that have shown that channel degradation to due to hydromodification occurs at relatively low levels of imperviousness (Hawley and Bledsoe, 2011;Hawley, Bledsoe, Stein, & Haines, 2012;Vietz et al, 2016).…”

Section: Local Applications Provide Insight Into Developing Regionasupporting

confidence: 88%

Application of regional flow‐ecology relationships to inform watershed management decisions: Application of the ELOHA framework in the San Diego River watershed, California, USA

et al. 2017

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Relationships between changes in streamflow and changes in biological condition are important considerations for water resources management decisions. The Ecological Limits of Hydrologic Alteration (ELOHA) framework offers a way to protect stream health by managing flow conditions. We demonstrate application of a regionally derived ELOHA framework to inform stakeholder defined management challenges in the San Diego River Watershed in southern California, USA-a large semi-urbanized watershed that is undergoing land use changes. Using previously defined flow-ecology relationships based on benthic invertebrate community composition, we: (1) assess how future land use changes will affect flow conditions and impact biological endpoints in the watershed; (2) demonstrate how flow-ecology relationships can be used to prioritize regions of the watershed into various flow management classes that can inform future planning decisions; and (3) evaluate how two future management decisions (specifically, modification of reservoir operations and implementation of low impact development strategies to reduce stormwater runoff) will affect in-stream flow conditions in the watershed. Our study shows a successful transition of regionally derived flow targets to inform local decisions at a catchment or watershed scale, thereby avoiding the need to develop local flow-ecology relationships for every stream of interest (as would be required by other instream flow methods). Case studies are a critical bridge between the science of flow-ecology and real-world implementation, and this work illuminates an example of how to navigate technical and management challenges and provide road maps for broader applications by including local stakeholders in defining, interpreting, and implementing products of flow-ecology analyses. KEYWORDS benthic macroinvertebrates, ecohydrology, ELOHA, in-stream flows, stream health, water resources management

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Section: Local Applications Provide Insight Into Developing Regionasupporting

confidence: 88%

Application of regional flow‐ecology relationships to inform watershed management decisions: Application of the ELOHA framework in the San Diego River watershed, California, USA

et al. 2017

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“…These riverine parks are meant to maintain ecosystem services for residents by reducing flooding risks, supporting a more natural ecosystem and providing recreational opportunities. Such morphologic change is part of an 'urban stream syndrome' that includes elevated concentrations of nutrients and contaminants and reduced biotic richness (Meyer et al, 2005;Walsh et al, 2005;Vietz et al, 2014). Channel instability and enlargement is endemic (Hammer, 1972;Booth, 1990;MacRae and Rowney, 1992;Pizzuto et al, 2000;Bledsoe and Watson, 2001;Chin, 2006), even where the extent of impervious cover is relatively low (Galster et al, 2008;Hawley and Bledsoe, 2011).…”

Section: Introductionmentioning

confidence: 99%

Enlargement and evolution of a semi‐alluvial creek in response to urbanization

Bevan

MacVicar

Chapuis

et al. 2018

Earth Surf Processes Landf

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The impact of urbanization on stream channels is of interest due to the growth of cities and the sensitivity of stream morphology and ecology to hydrologic change. Channel enlargement is a commonly observed effect and channel evolution models can help guide management efforts, but the models must be used in the proper geologic and climatic context. Semi‐alluvial channels characterized by a relatively thin alluvial layer over clay till and a convex channel profile in a temperate climate are not represented in currently available models. In this study we: (i) assess channel enlargement; and (ii) propose a channel evolution model for an urban semi‐alluvial creek in Toronto, Canada. The system is 90% developed with an imperviousness of approximately 47%. Channel enlargement is assessed by comparing 50 year old construction surveys, a recent survey of a relic channel, low‐precision surveys of channel change over a 15 year period, and high‐precision surveys over a three year period. The enlargement ratio of the channel since 1958 is 2.6, but could be as high 8.2 in comparison with the pre‐urban channel. When the increase in flow capacity is considered, the enlargement ratio is 1.9 since 1958 and up to 6.0 in comparison with the pre‐urban channel. Channel enlargement continues in the contemporary channel at an estimated rate of 0.23 m2/year. A five stage model is presented to describe channel evolution in the lower reaches. In this model the coarse lag material from glacial sources provides a natural resilience to the bed and incision occurs only after the increased flows from urbanization are combined with higher slopes as a result of channel straightening or avulsions. Further research should be done to assess stream behaviour close to an identified geologic control point. Copyright © 2018 John Wiley & Sons, Ltd.

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“…Given that around 90% of natural channels in the catchment have been converted to pipes (see Figure ), and the open channel that remains is armoured and stable, channel erosion is not a major component of the sediment budget. Direct human interventions to stabilize channels or increase flood conveyance are common in developments older than 5–10 years (Hawley et al, ), or with EI greater than ~10% (Vietz et al, , ). Scotchmans Creek, with development age of 50+ years and EI approaching 50%, is well within that realm where much of the channel has undergone rock protection as a response to erosion, and so the legacy is a moribund channel with little erosion.…”

Section: Discussionmentioning

confidence: 99%

A suburban sediment budget: Coarse‐grained sediment flux through hillslopes, stormwater systems and streams

Russell

Vietz

Fletcher

2019

Earth Surf Processes Landf

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Sediment in urban stormwater systems creates a significant maintenance burden, while a lack of coarse‐grained bed sediment in streams limits their ecological value and geomorphic resilience. Gravel substrates, for example, provide benthic habitat yet are often scoured from the channel bed only to end up in a detention basin or treatment wetland. This dual problem of both ‘too much’ and ‘too little’ coarse‐grained sediment reflects a watershed sediment budget that is profoundly altered. We developed a conceptual urban coarse‐grained (>0.5 mm) sediment budget across three domains: hillslopes (urban land surfaces), the built stormwater network and stream channels. We then quantified key sources, sinks and storages for a suburban case study, using a combination of hillslope and in‐channel monitoring, and interrogation of local government records. Around 36% of the sediment supplied to the stormwater network reached the catchment outlet, a level of sediment delivery much higher than observed in similar‐sized natural catchments. The remainder was deposited in the sediment cascade and either stored, or extracted and removed from the catchment (e.g. material deposited in sediment ponds and gross pollutant traps). Conventional urban drainage networks are characterized by high hillslope sediment supply and low storage, resulting in efficient sediment delivery. Channel erosion, deposition in (and extraction from) pipes and channels, and floodplain deposition are small compared to sediment transport through the cascade. An understanding of the sediment budget of urban headwater catchments can provide stormwater and waterway managers with the information they need to address specific sediment problems such as sedimentation in stormwater assets and geomorphic recovery of urban streams. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

show abstract

Ecologically relevant geomorphic attributes of streams are impaired by even low levels of watershed effective imperviousness

Cited by 98 publications

References 63 publications

Application of regional flow‐ecology relationships to inform watershed management decisions: Application of the ELOHA framework in the San Diego River watershed, California, USA

Application of regional flow‐ecology relationships to inform watershed management decisions: Application of the ELOHA framework in the San Diego River watershed, California, USA

Enlargement and evolution of a semi‐alluvial creek in response to urbanization

A suburban sediment budget: Coarse‐grained sediment flux through hillslopes, stormwater systems and streams

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