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.

(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.

Lakes are by definition water retention facilities; they store water (for flood control) and provide water for many purposes such as water supply, irrigation, fisheries, tourism, etc.ﾠ In addition, they serve as sinks for carbon storage and provide important habitats for numerous species of plants and animals, including waders.ﾠ In the past, lakes have sometimes been drained to free the land for agriculture purposes, or have simply not been maintained and have silted up.ﾠ Restoring lakes is re-introducing them where they have been in former times or revitalising them.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Early sowing refers to sowing up to six weeks before the normal sowing season.ﾠ This allows for an earlier and quicker development of crops and of a root network that leads to soil protection.ﾠ The period in which the soil lies bare is shorter and, therefore, erosion and run-off are less significant and water infiltration is improved.ﾠ Early sowing can also help to mitigate the extreme ETP rates typical of Mediterranean summers.ﾠ However, early sown plants are frost sensitive; therefore farmers run the risk of losing the crops because of the low temperatures.ﾠ In northern countries, temperature in spring (March) can be adequate but the risk of frost is still serious until May.ﾠ Therefore, early sowing requires specific tools (plastic tunnel covers, onsite green house, etc.) and cannot be applied by any farmers for any crops.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

To ease the overall functioning of the river, some hydrographical network elements could be reconnected, including the so-called hydraulic annexes. This will allow for improvement of lateral connectivity, diversifying flows and habitats, but also cleaning the secondary arms that play a key role for retention in high water periods.
- 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

The design and material used in forest road building may have strong impact on erosion risk and water quality in streams. Bridges or culverts used at stream crossings must be properly designed to minimise negative impacts on the aquatic environment. Poorly designed or poorly constructed stream crossings can lead to increased sediment mobilisation, changes in flow patterns and even flooding upstream if insufficient water is transported.

Properly designed stream crossings permit the free movement of fish and aquatic invertebrates and will not restrict peak flows. Ensuring that stream crossings do not restrict peak flows will help to reduce localised flooding and can ultimately be more cost effective as they will not need to be rebuilt following high flow events.

The sloping side of any hollow in the ground, especially when bordering a river. 

Continuous cover forestry (CCF) is a broad term encompassing a wide variety of forest management practices. One key feature of is that biomass removal is based either on small clearcuts or selective harvesting. Smaller clearcuts may create less hydrological disturbance but some of the filtration benefits associated with forest soils may be lost as a result of the greater driving and road maintenance needed for continuous harvesting.
- Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

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