Principles for urban stormwater management to protect stream ecosystems

Abstract

Urban stormwater runoff is a critical source of degradation to stream ecosystems globally. Despite broad appreciation by stream ecologists of negative effects of stormwater runoff, stormwater management objectives still typically center on flood and pollution mitigation without an explicit focus on altered hydrology. Resulting management approaches are unlikely to protect the ecological structure and function of streams adequately. We present critical elements of stormwater management necessary for protecting stream ecosystems through 5 principles intended to be broadly applicable to all urban landscapes that drain to a receiving stream: 1) the ecosystems to be protected and a target ecological state should be explicitly identified; 2) the postdevelopment balance of evapotranspiration, stream flow, and infiltration should mimic the predevelopment balance, which typically requires keeping significant runoff volume from reaching the stream; 3) stormwater control measures (SCMs) should deliver flow regimes that mimic the predevelopment regime in quality and quantity; 4) SCMs should have capacity to store rain events for all storms that would not have produced widespread surface runoff in a predevelopment state, thereby avoiding increased frequency of disturbance to biota; and 5) SCMs should be applied to all impervious surfaces in the catchment of the target stream. These principles present a range of technical and social challenges. Existing infrastructural, institutional, or governance contexts often prevent application of the principles to the degree necessary to achieve effective protection or restoration, but significant potential exists for multiple co-benefits from SCM technologies (e.g., water supply and climate-change adaptation) that may remove barriers to implementation. Our set of ideal principles for stream protection is intended as a guide for innovators who seek to develop new approaches to stormwater management rather than accept seemingly insurmountable historical constraints, which guarantee future, ongoing degradation.

Improving the Multi-Objective Performance of Rainwater Harvesting Systems Using Real-Time Control Technology

“…Therefore, the application of allotment-scale RWH systems has great potential to simultaneously reduce or eliminate excess runoff volume and provide water conservation benefits, while also mimicking natural baseflow regimes by means of carefully controlled discharge [10,[33][34][35]. There are two innovative RWH systems that can deliver these multi-objectives: the passive release system and the active release system.…”

Restoring in‐stream habitat in urban catchments: Modify flow or the channel?

“…This has led to calls for a catchment‐scale mitigation of hydrologic disturbance to address urban stream impairment (Askarizadeh et al, ; Burns et al, ; Loperfido, Noe, Jarnagin, & Hogan, ). It is argued that this management approach is necessary to restore the water quality and hydrological regimes needed to support healthy streams (Fletcher et al, ; Vietz, Rutherfurd, Fletcher, & Walsh, ; Walsh et al, ).…”

Restoration of contaminated ecosystems: adaptive management in a changing climate

“…For example, monitoring for more than a decade informed Stewart Lake stakeholders that selenium concentrations in water were reducing aspects of exposure, but technology to reduce sediment concentrations was inadequate. On the other hand, newer technologies applied in the Melbourne case provided a testable situation where water quality was improved and natural hydrology mimicked to support a potential return to good ecological condition (Walsh et al ). The Melbourne case also emphasized the value of a landscape perspective as controls were outpaced by new developments that added to nutrient and contaminant discharges.…”

“…These early findings have been sufficient to encourage broader adaptive stream and catchment management in the Melbourne region, with Melbourne Water initiating a program of dispersed SCMs in a second catchment (also being monitored for hydrologic and ecological response), testing an alternative governance approach to community engagement in SCM implementation (Prosser et al ). A preliminary conclusion of both studies has been that finding sufficient harvesting demand to reduce run‐off volumes required for restoration (Walsh et al ) is a major challenge using dispersed SCMs.…”