"Measures to reduce the flow into natural or artificial drainage systems, such as overland flow interceptors and / or storage, enhancement of infiltration, etc and including in-channel , floodplain works and the reforestation of banks, that restore natural systems to help slow flow and store water." (EC 2013: Guidance for Reporting under the Floods Directive)
River restoration contributes to flood risk management by supporting the natural capacity of rivers to retain water. As flood risk consists of damage times occurrence, flood risk management needs to reduce either the damage, or the likelihood of floods to occur, or both. River restoration reduces the likelihood of high water levels, and improves the natural functions of the river at same time.
The 6,300 km long Yangtze River in China was facing a reduction of wetlands areas and flood retention capacity. In 2002, the World Wide Fund for Nature (WWF) initiated a programme to reconnect lakes in Hubei
Province to the Yangtze River through opening the sluice gates and facilitating sustainable lake
management. These wetlands can store floodwaters and therefore reducing vulnerability to flooding in the central Yangtze region.
Floodplain or riparian forests can be extremely important for the prevention of floods and landslides. Floodplain forests used to be widespread in Bulgaria, but today they are only partially preserved. WWF, in partnership with local Bulgarian partners began a project for restoration and conservation of natural riparian forests of native species along the rivers Danube and Maritsa.
Saltmarsh and mudflats are usually located together with mudflats in front of the saltmarsh. Saltmarsh vegetation and saltmarsh creeks help manage floods by dissipating wave and tidal energy. They are valuable barriers to the risks of flood, as they dissapte wave and tidal energy. Saltmarshes used in combination with other measures can have beneficial outcomes to managing climate change impacts. Even a small width of fronting saltmarsh can significantly reduce the height of sea walls required to achieve the same level of protection and thus also reduce initial construction costs. Having saltmarsh fronting will also significantly reduce maintenance costs due to the reduced exposure to wave and tidal energy.
Riparian buffers are vegetated, often forested, areas (“strips”) adjacent to streams, rivers, lakes and other waterways protecting aquatic environments from the impacts of surrounding land use (Enanga et al. 2010). Use of riparian buffers to maintain water quality in streams and rivers is considered to be a best forest and conservation management practice in many countries and is mandatory in some areas.
Wetland restoration can serve to reduce coastal flooding and erosion. It has also additional benefits like provide new habitats or improve the landscape for recreational purposes. Wetland restoration relates to the rehabilitation of previously existing wetland functions from a more impaired to a less impaired or unimpaired state of overall function.
Reafforestation and afforestation refer to to activities where trees are established on lands with no forest cover. The concept of reafforestation is usually used in reference to areas where there was recent forest cover. Reafforestation and afforestation activities, as well as existing forests, can help to reduce the occurrence and intensity of floods.
A temporary flood barrier is one that is only installed when the need arises (that is, when high flood levels are forecast). A demountable flood defence is a particular form of temporary defence that requires built-in parts and therefore can only be deployed in one specific location. The removable stoplog defence is a particular form of demountable defence applicable only for small openings in a permanent defence. The more commonly adopted gate option for closing off a gap in a floodwall is neither temporary nor demountable, as it is part of the permanent defence and is left in place all the time (albeit normally in an open position).
If fluvial systems don't have sufficient room for natural detention of floodwater in the floodplain, the development and management of flood storage within and adjacent to the natural floodplain is recommended and described in more detail in this measure. It addresses aspects like the process of selecting where to locate the flood storage, deciding how much storage is needed, how to measure the storage capacity, selecting appropriate flow control structures, analysing how the works will perform and making sure that the flood storage scheme is safe in extreme floods.