Abstract
Climate changes and urbanization push cities to redesign their drainage systems, which may increase separate stormwater discharges to local recipients. In the EU, regulation of these is governed by the Water Framework Directive (WFD) and the Floods Directive, but national implementation varies and is often supplemented with local non-legislative guidelines. By reviewing trends and discrepancies in the Danish regulation practice for separated stormwater discharges, this article investigates how the directives are put into effect. A legislative gap for separate stormwater discharges introduces uncertainty in the discharge permit conditions, which especially affect conditions targeting water quality. We point to several topics to be addressed, e.g., the level at which the regulation of separate stormwater discharges takes place, opportunities for coordination with flood risk and climate change adaptation initiatives, as well as uncertainties regarding the application of Best Available Techniques. Working with these issues would elevate the regulation practice and aid regulators in reaching a more holistic and consistent approach, thus improving chances of reaching the desired recipient status before or after the WFD deadline in 2027. This could be undertaken at river basin, river basin district or national level, but there is also potential for harvesting mutual benefits by addressing these challenges internationally.
Highlights
Act [41] and the Water Planning Act [44]. These laws constitute the legal foundation for the Danish River Basin Management Plans (RBMPs), which contain an overview of the current status in the water environment, environmental objectives and a Program of Measures (PoM), and as such serve as an information tool on the Water Framework Directive (WFD) implementation progress
The conditions put forth in the reviewed Danish discharge permits could generally be divided into three categories: (1) peak flow control requirements, which put a limit on the maximum discharge from the outlet point to the recipient and require the detention of excess flow upstream from the discharge point; (2) Best Available Techniques (BATs) requirements, where a certain technology type and performance level is demanded for managing the discharge; (3) and ELV requirements that limit the outlet of specific substances to certain maximum concentrations or total loads
The WFD implementation in Denmark has resulted in a regulatory framework, where environmental impacts of separate stormwater discharges are mentioned as pressures in the RBMPs, but are completely overlooked in the associated PoMs
Summary
Initiatives to mitigate urban flood risk often affect the local recipients in terms of changed runoff patterns and reduced water quality, occasionally referred to as the “urban stream syndrome” [1].In order to protect the natural water systems from unwanted effects of stormwater discharges, while at the same time ensuring the efficient drainage of urban areas, it is necessary to implement technical solutions that can balance these, sometimes competing, agendas (Figure 1).Sustainability 2020, 12, 6317; doi:10.3390/su12166317 www.mdpi.com/journal/sustainabilitySustainability 2020, 11, x FOR PEER REVIEWIllustrationofof balancing act between accommodating theforneed for protecting the natural waters andwaters the need for effective management of stormwater in urban areas.receiving natural and the need for effective management of stormwater in urban areas.Worldwide, increasing urbanization [2] and land use changes negatively impact the nearby natural waters that receive the stormwater [3,4,5]. negatively The EuropeanUnion at large has Worldwide, [2][2]anddischarges landland use changes impact the nearby. Initiatives to mitigate urban flood risk often affect the local recipients in terms of changed runoff patterns and reduced water quality, occasionally referred to as the “urban stream syndrome” [1]. In order to protect the natural water systems from unwanted effects of stormwater discharges, while at the same time ensuring the efficient drainage of urban areas, it is necessary to implement technical solutions that can balance these, sometimes competing, agendas (Figure 1). Illustrationofof balancing act between accommodating theforneed for protecting the natural waters andwaters the need for effective management of stormwater in urban areas. Receiving natural and the need for effective management of stormwater in urban areas. Worldwide, increasing urbanization [2] and land use changes negatively impact the nearby natural waters that receive the stormwater [3,4,5]. Anddischarges landland use changes impact the nearby
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