Environment |
same time making a contribution to nature recovery, pollution prevention, soil protection, drought resilience, amenity value and carbon sequestration. “Our country faces several major environmental
threats, and we cannot solve them one at a time,” Mark Lloyd, CEO of Rivers Trusts said. “Managing landscapes to store more water provides multiple benefits to society, and can therefore attract multiple sources of funding. This pilot programme needs to become business as usual urgently and we need to break down the barriers to delivery at scale.” The government has a target of doubling the number of natural flood management projects over the next five years and is investing £5.2 billion in flood and coastal defences to ensure more communities are better prepared – and nature-based solutions are a key component of this.
Mega flood Back in the US, with drought and wildfire becoming
increasingly more prevalent and receiving more attention throughout California, there is a fear that Californians may now underappreciate the risk the region faces from severe but infrequent flooding. According to a new paper from Xingying Huang and Daniel Swain in Science Advances, climate change is increasing the risk of a Californian mega flood. “California is a region more accustomed to water
Above: Flooding in California during 2019. Although the region is more accustomed to water scarcity, a growing body of research suggests that climate change has already increased the risk of a trillion- dollar mega flood occurring Credit: Gibson Outdoor Photo /
Shutterstock.com
j
we must use every weapon in our armoury and natural flood management will play an essential role in this. By harnessing the power of nature alongside our traditional flood defences, we can not only help keep communities safer, but also create wildlife havens and tackle the climate emergency.” Natural flood management measures include
planting trees and hedges to absorb more water, creating leaky barriers to slow water flow in streams and ditches and restoring salt marshes, mudflats, and peat bogs. In Cumbria, a project trailed a variety of measures across different landscapes aiming to slow or store 10,000 cubic metres of water per square kilometre. The team worked with a range of landowners and the Forestry Commission to change overland flow routes, build earth dams and leaky barriers, plant 8000 trees and create offline flood storage ponds.
Meanwhile, the community-led Shipston Area Flood Action Group used measures across the River Stour in Warwickshire to create 700 leaky barriers and ponds to slow the flow of water during heavy rainfall, reducing the flood risk to people and businesses in 17 villages and towns. The Rivers Trusts says natural flood management
has a really important role to play in protecting communities from the misery of flooding, while at the
References
Drought in southwest China – more hydropower is the solution to drought by Victoria Cardenas, Senior Communications Officer at the International Hydropower Association (IHA). Blog 20/11/22.
www.hydropower.org
Climate change is increasing the risk of a California megaflood by Xingying Huang and Daniel L Swain. Science Advances. 12 Aug 2022. Vol 8, Issue 32. DOI: 10.1126/sciadv.abq0995
Climate change makes catastrophic flood twice as likely by David Colgan, Director of Communications, Institute of the Environment and Sustainability in California. 8.12.2022 www.
ioes.ucla.edu/article/climate-change-makes-catastrophic-flood-twice-as-likely/
36 | February 2023 |
www.waterpowermagazine.com
scarcity than overabundance in the modern era. Between 2012 and 2021, California experienced two historically severe droughts – at least one of which was likely the most intense in the past millennium – resulting in widespread agricultural, ecological, and wildfire-related impacts and ongoing drought-focused public policy conversations,” the authors stated. Huang and Swain went on to discuss The Great Flood of 1861–1862 where weeks of winter storm events produced widespread catastrophic flooding across virtually all of California’s lowlands. A temporary but vast inland sea of floodwaters was up to 480km long and 96km across. Back then the population was approximately 500,000 but today it is nearer to 40 million. A growing body of research now suggests that
climate change has already increased the risk of another mega flood scenario in California and that “future climate warming will likely bring about even sharper risk increases”. The authors said that runoff in a future extreme storm scenario is 200-400% greater than in historical values in the Sierra Nevada, due to increased precipitation rates and decreased snow fraction. Estimates suggest that a modern-day mega flood would be a US1 trillion-dollar disaster, larger than any in world history. Every major population centre in California would get hit at once, along with other adjacent states. Relief efforts would be complicated as major roads could be shut down for weeks, or even months, while there would be global impacts on economic and supply chains. It would also be practically impossible to evacuate up to ten million people who could be displaced by the flood waters, even with weeks of notice from meteorologists and climatologists. Further inter-agency collaboration and research is
planned to try to map out where flooding could be worst and to help inform state-wide mitigation plans, such as drawing down reservoirs in preparation or inundating dedicated flood plains. ●
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