What’s not to love about trees? They regulate the earth’s climate, clean the air of pollutants, absorb carbon dioxide and give us oxygen to breathe, provide habitat for wildlife, regulate flood waters, and much more.
At the Sussex Flow Initiative (SFI), we are interested in all of the benefits that trees provide, but we are particularly excited about their potential for reducing flood risk, as well as making our landscapes more resilient to drought. The benefits wheels below (taken from the Environment Agency’s Working with Natural Processes evidence base) help to illustrate just how many benefits woodlands can have across a whole range of important natural life support systems.
The ability of trees to control flood water is the result of their importance within the hydrological cycle; intercepting rainfall, taking up water from the soil, slowing down surface run-off, and promoting water infiltration and percolation into soil and groundwater. These processes hold water on land, and reduce the amount and speed of the delivery of water to our streams and rivers. The evidence for catchment-wide woodland reducing flood flows is strong, with research able to show the negative impacts that woodland felling has at a catchment scale, on stream discharge and sediment delivery.
With this in mind, SFI have been making sure that we plant trees in the right places, wherever we can, to help reduce flooding. We have planted our fair share of trees throughout the Ouse catchment since the project started in 2012 – over 28,000 in fact. In December 2017, we embarked on our largest tree planting project to date – the planting of a further 12,050 trees (bringing our 2017/18 total to 17,900!) in the form of 2km of hedgerow and 1.3 hectares of woodland at the Sussex Horse Rescue Trust in Uckfield. The site is a fantastic location nestled between areas of ancient woodland and park land, with large fields sloping down to the floodplain of the River Uck – an ideal location for natural flood management enhancements, which will also provide important corridors for wildlife to move between the surrounding sites.
With the help and support from the local community and dedicated volunteers from the surrounding areas, we are pleased to say that we planted the last of the trees this week! With over 800 hours of volunteer time (from more than 125 volunteers), we really couldn’t have done it without them, and hopefully they will find the time to revisit the site in years to come to see the transformation once the trees are established. Working with these volunteers, and the landowner who appreciates the importance of these features of the landscape has been a fantastic experience, and we are already looking forward to next seasons planting at the site (a further 1.5km of hedgerow and more woodland areas), and reconnecting with the volunteers on other projects after a well-deserved rest.
Last week we posted a blog about our working washland near Plumpton. One week on and our working washland is complete. The weather has obliged us by raining heavily for a few days, filling it with water, so that we can show you exactly how it works.
When you look at the site, you would never imagine that such a small, innocuous valley could make such a huge contribution to reducing flooding locally, and to biodiversity. But witnessing just one of these projects in action makes you realise just how easy it would be to capture and store millions more litres of water in our countryside, in flood storage that would benefit people and wildlife.
At the final count, the additional flood water storage water that the site creates is a whopping 350,000 litres (350 tonnes) of water, and that’s BEFORE the site floods! Once it floods, the flood storage in the valley could be anything from around 350,000 litres to 1,350,000 litres of extra flood storage, depending on the height of the flood. This flood water is slowed down and spread out across the land, allowing silt and other debris to drop out of the water, making it a much less dangerous flood peak, benefitting soil fertility and reducing pollution and siltation in our rivers.
When we started this project, we thought that the majority of the water flowing into the site would be flood overflow from an adjacent stream. What has happened instead is that it has filled up rapidly from rainfall running off the surrounding grassland slopes. This is particularly interesting. In a natural meadow like this, it is widely accepted that the rough grassland will slow
down rainfall enough to enable most of it to filter into the soil and away into aquifers rather than flowing over the land surface. However, the intensity of the rainfall meant that instead, there was very obviously a lot of overland surface water flooding filling up the new washland, way before any actual river flooding took place. The soil on the site is some of the best I’ve seen, so it is not soil compaction creating this flood run off, it is simply the volume of water falling onto the slope in a short space of time.
So our new washland is helping to store both river and ‘land’ flooding, and in doing so is creating some really nice restored wetland habitat. Seeing so much water appear in the washland overnight was fantastic. I can’t wait to see what wildlife shows up next spring.
What does Natural Flood Management look like on the ground? There are all sorts of things we can do to slow and store water in our landscapes – planting trees and hedgerows, digging ponds, putting natural wood back in streams and more. We can also restore natural washlands – but what are they?
Washlands are areas of land where water can spread out, slow down and be stored temporarily, whilst it’s flooding. Some of the biggest potential for storing excess flood water when it’s raining hard is in our smaller stream floodplains. These are often where the land use is less intensive, and where there is space for water to come and go periodically without adversely affecting people and farming.
Water follows the line of least resistance. If we can create those lines of least resistance in the right places, then suddenly water is flowing into all the areas we want it to, rather than into our houses. At the same time, we can provide climate regulation, water purification, pollination, wildlife habitat, better green spaces for people and much more.
This week we spent a couple of days with an obliging landowner and a digger, restoring the relict course of an old chalk stream. Diverted decades ago to feed a local mill, the old stream bed only really gets wet now when it floods. The local landowner saw the potential to make the stream a more active flood relief channel, and we went to work.
It’s been fantastic watching it take shape. All we needed to do was to make it easier for the flood water to find the old stream channel, and the water and natural gravity will do the rest. We’re only half way through the project, and already we have created around 100 tonnes of extra flood water storage, as well as a fantastic area of habitat for wetland wildlife.
... now we just need some rain to check that it works !!
The Sussex Flow Initiative has achieved a huge amount since it began 5 years ago, working with local communities, councils and organisations to investigate the potential for natural flood management, and to naturally reduce flood risk across the County and beyond.
In 2012, the Sussex Wildlife Trust, Environment Agency and the Woodland Trust began an innovative project in the River Ouse catchment in Sussex - the Sussex Flow Initiative (SFI). The project’s role was to investigate opportunities for Natural Flood Management (NFM) at the catchment scale, and to implement a range of different techniques to naturally reduce flood risk whilst providing multiple benefits to society and the environment.
In its first 5 years, we advised 150 landowners on over 5,650 hectares of land, planting nearly 28,000 trees and creating over 1,000,000 litres of new seasonal water storage by constructing flood storage ponds, pocket ponds and other Run-off Attenuation Features. Working with the Ouse & Adur Rivers Trust we helped to map nearly 5,000 ha of the catchment, and have facilitated River Habitat Surveys along 51 km of main rivers, resulting in detailed sub-catchment plans that will help target our future work.
The project is not only helping to reduce flood risk for communities downstream, it is also contributing to vital wildlife networks, and is enhancing a variety of ecosystem services, such as water purification, aquifer recharge, and climate regulation. We estimate that we have helped to store at least 10,000 tonnes of CO² in 5 years.
By disseminating information on NFM in the form of published guidance and handbooks, the SFI website and social media, as well as newspaper articles and features on local radio, the project has had far-reaching influence, as well as helping to support others to use an NFM approach. Over the last 5 years, SFI has developed strong partnerships and collaborations with organisations and academic institutes throughout the UK, supporting the development of computer models and NFM targeting tools, and research into the design and influence of large woody debris on flow and geomorphology.
One of the (not so) secrets of success of SFI, and NFM more generally, is the willingness of local communities to take ownership of tackling flood risk, either by carrying out work on their land or volunteering their time to help. We’ve been only too happy to help support these communities to feel empowered to do something tangible to help reduce flooding in their local area. We’ve also clocked up over 150 volunteer workdays, involving a range of activities from GIS mapping to tree planting. We are very grateful for all this support - the project couldn’t have come this far without its volunteers.
Through working closely with local landowners, communities, councils and organisations, the SFI project has been a huge success and continues to deliver advice and practical implementation of NFM throughout Sussex. SFI has had a busy five years (full 5-year report available here) and with national interest in NFM growing, we have even more ambitious plans for the next five years. So keep your eyes out for our 5-year vision, and for our contribution to natural flood management over the next few years, as well as a national programme of natural flood management supported through the Environment Agency’s Working with Natural Processes Project!
Environment Agency publishes report on Natural Flood Management evidence base
For a while now, local projects have been making our landscapes more flood resilient at a local level, and showing that working with natural processes really can help to reduce flooding. Until now however, there has been no national platform bringing us all together to share and embed Natural Flood Management as a national discipline. On the 31st of October at the CIWEM conference, the Environment Agency launched their much anticipated ‘Working with Natural Processes’ (WwNP) report, which brings together all our evidence and expertise into one easily accessible national resource.
The WwNP documents are an invaluable resource for flood risk managers and those advocating and implementing Natural Flood Management (NFM). The reports provide an in-depth review of the existing evidence for NFM; providing summaries of the main types of NFM; key literature; the level of confidence in each NFM approach, and identifying the gaps in our knowledge. The report is accompanied by interactive maps for targeting NFM and an extensive selection (65!) of case studies throughout the country.
The good news is that an analysis of vast wealth of existing research reveals that NFM can definitely help to reduce flood risk, particularly for smaller magnitude floods in small to medium sized catchments. The report also shows that NFM provides multiple additional benefits both to the environment (e.g. habitat creation, water quality improvements, climate regulation), and to society, through reduced flood risk, increased access to green space, creating a healthier environment etc.
Importantly, the knowledge gaps that were identified, such as how NFM can mitigate extreme flood events or how it can provide climate change resilience, will shape future research projects, which will continue to feed into the evidence base for NFM. In fact, the Environment Agency and the Natural Environment Research Council have put together a £3.4m research call to fund projects that contribute to further understanding of NFM. One of the key areas where further evidence is needed is the use of NFM in lowland catchments, which the SFI project is helping to provide.
The report offers a range of “Top tips” for utilising NFM, all of which are at the core of the work that we do at the Sussex Flow Initiative :-
We already work closely in partnership with the Environment Agency on the SFI project, but we look forward to working with them more closely to embed NFM in all Flood Risk Management projects and strategies.
The full report and accompanying resources can be accessed here
We are pleased to welcome Matt as our new Project Officer for SFI. He will be continuing our work in the Ouse catchment to reduce flood risk using Natural Flood Management (NFM). He brings a wealth of enthusiasm and skills to the position, including research expertise in freshwater ecology, hydrology, and geomorphology, an understanding and appreciation of the multiple benefits of Natural Flood Management, as well as lots of practical skills that will ensure Sussex Flow Initiative (SFI) can meet their ambitious targets for 2017/18 and beyond!
We’ve got lots of plans and ideas for NFM within the Ouse catchment, so if you would like to discuss the potential for NFM on your land, you have any questions about NFM, or if you’d like to get involved as a volunteer, please get in touch with us at firstname.lastname@example.org