When considering flood management strategies, ideas typically revolve around constructing taller embankments, reinforced levees, and cement walls. However, could the optimal approach – beneficial for both communities and ecosystems – be to allow rivers more room rather than restricting their flow?
This alternate solution is gaining traction as a method for reducing flood risks. However, giving rivers more space to flow also provides additional benefits. ecological benefits well past just reducing flood risks. It aids in biodiversity, enhances water quality, and captures carbon.
With climate change exacerbating the occurrence and severity of extreme floods , reassessing our strategy for handling floodplain rivers has never been more pressing.
Climate change, flooding, and restricted rivers
Climate change is amplifying flood risks worldwide, and Aotearoa New Zealand is no exception Large-scale flooding is anticipated to become far more regular and intense , posing risks to communities, infrastructure, and ecosystems.
A lot of these risks are exacerbated by previous leadership choices those with rivers restricted into tight channels artificially, isolating them from their natural floodplains.
Floodplain river systems have historically been dynamic , transitioning through different terrains over time. However, extensive retaining walls, alterations to river channels, and land development have limited this natural variation.
Choking rivers in this manner redistributes and amplifies flooding hazards further downriver by pushing water through narrowed passages at higher velocities. This practice also deteriorates the ecosystems dependent on the natural rise and fall of river dynamics.
Allowing rivers room to spread
The concept of permitting rivers to resume control over areas on their natural floodplains is not novel.
In the Netherlands, the Room for the River The program emerged as a reaction to the floods in 1995, which resulted in extensive evacuations of both residents and livestock. In England, forecasts indicating that the financial hazards linked to flooding could rise twentyfold during this century have sparked initiatives. Making Space for Water strategy.
However, these initiatives typically stay concentrated on flood defense , missing chances to optimize ecological advantages. Our new research demonstrates that thoughtfully crafted strategies can provide both environmental benefits and flood defense.
This is essential as floodplain river systems rank amongst the most valuable ecosystems They offer approximately one-fourth of all terrestrial ecosystem services like water retention and contaminant filtering, along with providing educational opportunities, recreation, and cultural benefits. benefits .
Managing rivers for variability
A key transformation in managing rivers entails recognizing and adjusting to their inherent variability. Floodplain rivers do not remain constant; they evolve over space and time, reacting to seasonal water movements, sediment transport, and ecosystem dynamics. processes .
Our research summarizes the ecological activities triggered when floodplain rivers have space to spread out.
Rivers that have not been artificially restricted usually more physically complex For example, alongside the primary river channel, there could be narrower tributaries, spots where the flow collects and decelerates, underground springs emerging to merge back into the above-water currents, or even oxbow lakes within the surrounding plains.
A wide variety of environments sustains a abundant diversity of flora and fauna . Even gravel bars, which appear along free-flowing river systems, serve as crucial nesting grounds for endangered bird species.
Biodiversity isn’t uni-dimensional; rather, it functions across various levels, ranging from a tiny marshland pool to an extensive entire watershed or even broader areas. Within this evolving riverside environment, we could observe variations in the genetic makeup of a species differing throughout distinct sections of the river, or perhaps notice identical fish species showing regional disparities. differing in their bodily dimensions , based on the habitat conditions.
These instances of inherent biological variation allow species and ecosystems to remain adaptable when faced with unpredictable future circumstances.
On a broader scale, the variety and quantity of species inhabiting distinct floodplain river environments differ as well. Such biodiversity among ecological communities leads to this variation. variation in the functions Ecosystems function within the river, like absorbing nutrients or breaking down organic material. This capability can even assist with diversify food webs .
These differences imply that various species or groups within the river may not experience the same disruptions like droughts or floods simultaneously. The reason for this lies in how different plant and animal populations in rivers operate. evolved to take advantage In various manners, these patterns examine the extended cycles of flooding and water scarcity occurrences.
For example, the cottonwood trees in the southwestern United States synchronize their seed dispersal with the reliably recurring patterns of spring flooding caused by melting snow in that region. In Aotearoa New Zealand, certain whitebait fish species usually lay their eggs during strong autumn currents. These eggs later hatch into larvae that are carried out to sea via powerful winter flows.
Certain creatures require various environments along the river. different stages of life . Various animals journey long distances to utilize the river floodplains temporarily. This group encompasses the banded dotterel ( Charadrius bicinctus ), native to Aotearoa New Zealand. This bird journeys up to 1,700 kilometers for nesting Each spring, banded dotterels can be found on braided river gravels. These birds are declining in number, and they depend on river habitats that offer ample room to move around.
An appeal for enhanced eco-friendly river governance
With the acceleration of climate change, it becomes essential to reconsider our approach to managing water systems. While strengthening embankments and increasing channel depths might appear as sensible solutions for heightened flooding threats, such methods frequently exacerbate long-term vulnerabilities and transfer risk elsewhere.
We urge professionals to take action. expand the range of values incorporated into river management policies and programs to account for ecological variation.
Nature-based solutions These methods aim to enhance benefits for both humans and nature. By cooperating with natural processes instead of opposing them, we can develop environments that are stronger, more adaptable, and conducive to supporting both human needs and biodiversity.
The moment has come to adopt a fresh approach to managing our rivers—a strategy where we view these waterways not as hazards to subdue, but rather as vital resources essential for protection and rejuvenation.
Christina McCabe is funded via an Aho Hīnātore doctoral research scholarship at the University of Canterbury.
Jonathan Tonkin is funded by a Rutherford Discovery Fellowship and the Centre of Research Excellence Te Pūnaha Matatini. Additionally, he receives support from the Antarctic Science Platform as well as the Ministry of Business, Innovation and Employment.