Levelling longitudinal barriers allows re-establishing fluvial dynamics and ecological continuity. The aim is to restore the slope and longitudinal profile of the river, to restore natural water flows, to allow for the solid transport (sediment) to take place, toﾠ diversify flows (depth, substrate, speed), diversify habitats and related flora and fauna.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

AGR stores large quantities of water in underground aquifers to increase the quantity of groundwater in times of shortage.ﾠ It results in a lowering of run-off from surrounding land, and in an enhanced natural condition of aquifers and water availability.ﾠ The natural cleaning process of water percolating through the soils when entering the AGR improves water quality. Mechanisms used to undertake the recharge should be highlighted. In this respect one can envisage:(i) surface structures to facilitate/augment recharge (such as soakways and infiltration basins);(ii) subsurface indirect recharge - artificial recharge is undertaken through wells drilled within the unsaturated zone;(iii) subsurface direct recharge - artificial recharge is undertaken through wells reaching the saturated zone. The regulatory approach to be adopted for each of the above three mechanisms could differ considerably, due to the fact that the level of natural protection to groundwater is vastly different for each of the mechanisms

Shallow excavations filled with gravel or other material to create temporary storage and to enhance the natural capacity of the ground to infiltrate. Infiltration trenches would typically be used to intercept surface runoff drainage (e.g. drainage from roof or other impervious areas) or to convey water towards a detention pond.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

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.

The (monetary) value of resources deployed for the implementation of any NWRM, which includes upfront capital expenditures, either from new investments or the replacement of assets in past investments; depreciation allowances (annualised cost or replacing the accounting value of existing assets in the future); operating expenditures (those incurred to keep the NWRM running in an efficient manner); maintenance expenditures (for preserving existing or new assets in good functioning order throughout their useful life); and decommissioning costs (those incurred at the end of the lifecycle of the NWRM).

Sacrifice associated to the use of available resources to one means instead of another (so that any economic cost is indeed an opportunity cost) or of following one course of action instead of the best available alternative. As applied to NWRM, it refers to those negative impacts in terms of welfare, either direct or indirect, that may be linked to the implementation of any measure.
The difference between explicit and implicit costs depends on whether there is an unequivocal monetary payment (or at least one which is straightforward to infer) or not. The term ﾓdirect (economic) costﾔ does actually refer to those costs that fall directly on the promoter of the NWRM. Hence, as opposed to direct costs, indirect costs are those incurred by others (those who are not under the direct scope of the NWRM implementation).

Coarse woody debris is a key stream habitat feature used by fish and other organisms. Coarse woody debris can also help to lower flow velocity in streams.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Gently sloping vegetated strips of land that provide opportunities for slow conveyance and infiltration. Designed to accept runoff as overland flow from upstream and to slow the progress of this runoff.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

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

'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