This manuscript analyzes and discusses viewpoints concerning the renaturalization of floodplains as an instrument of management in large catchments, using natural flood defense schemes. Schemes consider the differentiated supply of ecosystemic services based on river channel/floodplain interactions. Conventional structural methods used to prevent flooding (e.g., longitudinal dikes) are increasingly showing themselves to be less efficient with regard to advances in the problems of environmental management of the territory, especially when combined with extreme events, where the importance of perfecting strategies for harmonizing duly controlled floodable areas and water retention can be seen. Natural flood risk reduction measures are part of a holistic solution for sustainable management of flood risk, conservation of nature, water quality and green economy. They rely upon the inherent ability of floodplains to retain water in the basin, and this can delay and reduce peak flows.
A floodplain is the region in a river valley surrounding the river that is flooded when river discharge is significant, and that consists of sedimentary material [
Humans have historically settled in floodplains, due to their modest declivity, highly fertile soils, and availability of water [
Conventional structural methods used to prevent flooding, such as longitudinal dikes, are often partly ineffective during catastrophic events because, aside from reducing the supply of ecosystem services, they affect the consequences of the problem, not its causes [
Currently, the conservation and restoration of floodplains are recognized as efficient and natural methods of management, and in some cases can substitute for classic engineering approaches [
For the renaturalization of floodplains to efficiently control floods, the different types of flooding in natural and artificial areas must be controlled, compatible land uses must be considered, and objectives must be integrated to optimize water interactions between the channel and the floodplain [
In central Europe, part of the floodplains of the Danube River was restored by removal of dams [
Developing countries, due to their unique cultural and economic issues, are often unable to implement floodplain renaturalization projects, however, there are exceptions (
Functionally operative floodplains provide important social benefits because they can control downstream flooding, and this can provide important economic benefits. The additional benefits include increased quantity and quality of water, biodiversity, organic material, retention of toxic substances, and interactions of water in the channel and floodplain. Floodplain renaturalization mitigates erosive processes on the riverbanks, reduces silting in the channels, and provides a refuge for fauna, thus improving the reproduction and survival of wildlife [
Natural flood risk reduction measures include protection of the hydrological functions of floodplains, reduction or removal of embankments, (re)construction of meanders and flowing side channels, construction of flood bypasses, altering the vegetation to modify hydraulic roughness, removal or lowering of groynes and other hydraulic obstacles in the river channel, and re-meandering the river course or allowing the development of spontaneous river morphology [
Renaturalizing a floodplain is more challenging when there have already been large-scale alterations of hydrologic regimes, which have led to unpredictable fluctuations in precipitation and flows [
A change in thinking is necessary to develop consensuses that the renaturalization of floodplains is a natural and sustainable method to mitigate the flooding of important areas. In particular, technical and structural solutions must yield to solutions that improve natural function and have flow risk management as an objective. Society must learn to live with controlled flooding and provide support for environmental services to guarantee their economic feasibility. Natural flood risk reduction measures are part of a holistic solution for sustainable management of flood risk, conservation of nature and water quality and a green economy, because they rely upon the inherent ability of floodplains to retain water in the basin, and this can delay and reduce peak flows.
For their support: the National Council for Scientific and Technological Development (CNPq), National council for the Improvement of Higher Education (CAPES) and the Federal Rural University of the Rio de Janeiro (UFRRJ).
Baptista, M.N. and Valcarcel, R. (2018) Renaturalizing Floodplains. Journal of Water Resource and Protection, 10, 533-537. https://doi.org/10.4236/jwarp.2018.105029