Search

(either positive or negative). Third-party effect or welfare impact, which is both unilateral (i.e. one cannot decide neither whether to suffer it or not nor how much impact to bear), and non-compensated. In other words, an externality stemming from the implementation of a NWRM is a cost (if negative) or a benefit (if positive), which is not directly reflected in the direct costs or benefits of the NWRM but are one of its outcomes. It is a welfare variation expressed in monetary units.

Urban forest parks or protected areas provide multiple benefits including increased water infiltration, pollutant filtration, reductions in peak flow and maintenance of base flows. Urban forests also have many other aesthetic, biodiversity and quality of life benefits.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

In the past, rivers have been straightened by cutting off meanders (historically, many rivers in northern and western Europe have been straightened and channelized to facilitate log floating and/or speed up the drainage of water and control/limit the river bed movements).ﾠ Re-meandering is bringing a river back closer to its naturally meandering state by creating a new meandering course and by reconnecting cut-off meanders.ﾠ Re-meandering slows down the flow of a river.ﾠ The new form of the river channel creates new flow conditions and very often also has an impact on sedimentation.ﾠ The newly created or reconnected meanders also provide habitats for a wide range of aquatic and land species of plants and animals.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Traditional terraces consist of nearly level platforms built along contour lines of slopes, mostly sustained by stone walls, used for farming on hilly terrain.ﾠ When properly built and well maintained, terraces can reduce erosion and surface run-off by slowing rainwater to a non-erosive velocity.ﾠ So-called traditional terracing involves less disturbance of the terrain than modern terracing, as it does not involve significant levelling or cutting using heavy machinery.ﾠ
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

'Hard-edged' conveyance channels to move water between components in a SuDS 'train'.ﾠ Typically narrower than swales, but may also include vegetated aspects.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Basins and ponds store surface run-off.ﾠ Detention basins are free from water in dry weather flow conditions but ponds (e.g., retention ponds, flood storage reservoirs, shallow impoundments) contain water in dry weather, and are designed to hold more when it rains.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Wetlands restoration and creation can involve: technical, spatially large-scale measures (including the installation of ditches for rewetting or the cutback of dykes to enable flooding); technical small-scale measures such as clearing trees; as well as changes in land-use and agricultural measures, such as adapting cultivation practices in wetland areas.ﾠ Wetland restoration can improve the hydrological regime of degraded wetlands and generally enhance habitat quality. (Creating artificial or constructed wetlands in urban areas can also contribute to flood attenuation, water quality improvement and habitat and landscape enhancement).
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Afforestation is the process of planting trees, either to replace those removed during forest harvesting or as a means of land use conversion. Afforestation is part of several natural water retention measures as it can contribute to a more natural and sustainable hydrologic cycle.

Negative impacts connected with the actual or potential degradation of natural assets or environmental quality due to economic activities.

Length of time for which the NWRM may fully operate.

Those expenditures that, once committed, cannot be (easily) recovered. These costs arise because some activities require specialized assets that cannot be readily diverted to other uses.

EU definition:
Green Infrastructure is addressing the spatial structure of natural and semi-natural areas but also other environmental features which enable citizens to benefit from its multiple services. The underlying principle of Green Infrastructure is that the same area of land can frequently offer multiple benefits if its ecosystems are in a healthy state. Green Infrastructure investments are generally characterized by a high level of return over time, provide job opportunities, and can be a cost-effective alternative or be complementary to 'grey' infrastructure and intensive land use change. It serves the interests of both people and nature.
Clarification points:
From the perspective of Natural Water Retention Measures (NWRM), green infrastructure refers to new methods of managing water, favouring as much as possible the restoration of natural ecosystems or at least of their key functionalities in terms of water management. It consists of land management or engineering measures which use vegetation, soils, and other natural materials to restore the natural water retention capacity of the landscape. Green infrastructure measures use natural and man-made materials to enhance or improve longitudinal and lateral hydrological connectivity and natural hydrologic processes, including infiltration and runoff control but also purification processes. Green infrastructure can exist at a range of spatial scales, ranging from the very local, to the scale of a neighbourhood, a city or a whole region.
Local scale green infrastructure includes green roofs, permeable pavements and downspout disconnections, all of which can contribute to greater natural infiltration, reduced load on wastewater management systems, and limitations of peak runoff.
At the scale of a city or neighbourhood, green infrastructure can support sustainable urban drainage systems that mimic nature by soaking up and storing water or biodiversity promotion with fish ladders.
At a regional scale, green infrastructure can include the mosaic of managed semi-natural and natural areas that provides habitat, flood protection, cleaner air, and cleaner water. Thus land management strategies such as afforestation and retention of natural water retaining features in agricultural areas such as riparian buffers, ponds and wetlands can be considered as Green infrastructures designed to manage flood risks in downstream urban areas.
One key feature of Green infrastructure is its multi-functionality. The underlying principle of green infrastructure is that the same area of land can offer multiple benefits if the natural or man-made ecosystem is in a socio-ecologically sustainable state. Benefits of green infrastructure include a more natural hydrological cycle and ecosystem services related to biodiversity and human amenity. Green Infrastructure investments are generally characterized by a high level of return over time, provide job opportunities, and can be a cost-effective alternative or be complementary to 'grey' infrastructure and intensive land use change. Green infrastructure serves the interests of both people and nature.

LID is a toolbox of site-scale practices that the site designer and developer can utilize to:

• manage urban rainfall where it occurs for minimized stormwater concentration and runoff
• potentially lower short-term and long-term development costs
• improve water quality
• enhance natural habitat and flood control
• improve green space aesthetics and potentially increase property values
• increase community quality of life and livability

There are many practices that are used to support these benefits, including bioretention systems, rain gardens, vegetated rooftops, bioswales, rain barrels, and permeable pavements to name a few. By implementing LID principles and practices, water can be managed in a way that reduces the impact of built areas on the environment while providing numerous additional benefits. (source: LID symposium).

This concept is very similar to NWRM in the United States context. It is very connected to Green Infrastructure. See also the link to US EPA green infrastructure website.

Shallow, broad and vegetated channels designed to store and/or convey runoff.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission