SH0083

Written Evidence submitted by the Floodplain Meadows Partnership (SH0083)

About The Floodplains Meadow Partnership

The Floodplains Meadow Partnership is unique in bringing together scientists and practitioners to develop an understanding of how to manage, restore and create floodplain meadows[1] and the multiple benefits they provide. The partnership is hosted by The Open University and supported by Natural England, the Environment Agency, the Centre for Ecology and Hydrology and several NGOs including the RSPB, The Wildlife Trusts, the Field Studies Council, the National Trust and People Need Nature.  https://www.floodplainmeadows.org.uk/

Introduction and key points

1)      We welcome the inquiry into Soil Health, which aims to investigate how the government intends to meet its goal of having all soil “managed sustainably” by 2030 and what role it and other stakeholders should play in preventing further soil degradation and restoring soils across England, including through its Environmental Land Management Schemes and Soil Health Action Plan for England ( SHAPE).

2)      We wish to draw attention to soil health on floodplains.  Alluvial soil is probably some of the most damaged soil within the UK – often compacted, lacking organic matter and affected by erosion and excess nutrients.  However, it is capable of delivering a wide range and high value of ecosystem services, if managed sensitively. 

3)      UK floodplains occupy around 652,000 ha, at least 70% of which no longer functions naturally, offering huge opportunities for conservation professionals to work together to restore a functioning mosaic of wetland habitats.

4)      We also wish to draw attention to the role which species rich grasslands can play in restoring soil health whilst remaining productive agricultural land.   Around 40% of the UK’s land surface is grassland, but this is vulnerable to disturbance and may not necessarily be managed in ways beneficial to the soil beneath.  Well managed species-rich grasslands are able to sequester carbon in their soils and to improve soil structure more effectively than most alternative land uses.

5)      We are disappointed that there is no reference to an action to develop the promised SHAPE within the Environmental Action Plan.  Healthy soils are key for nature recovery and the eco services we require.  We need a plan and in particular stress that any SHAPE should incorporate a strand of work around alluvial soil with a strategy to recognise their existing value (some alluvial soils can hold more carbon per unit area than a peat soil), to tackle risks, such as the disconnection of floodplains from their rivers, and to address the damage previously sustained.  Measures to achieve these aims should recognise the role of species-rich grassland habitats, such as floodplain meadows, within any action plans, monitoring and further research.

The importance of functioning floodplains

6)      Floodplains are vulnerable to climate change, which is already having a substantial impact on the communities, agricultural industry and biodiversity that depend on them.

7)      Floodplains face challenges from current practices (e.g. building flood embankments forever higher), which are harming the environment and are unsustainable

8)      Floodplains only cover 5% of the land area in England, yet their contribution to our natural capital is many times that figure.  They produce more food, hold more water, support more biodiversity, store more carbon and have greater aesthetic, social and cultural value than a typical piece of land outside a floodplain.  They are well mapped and should be regarded as a distinct land type with respect to laws pertaining to planning, agriculture, biodiversity and the wider environment, but in too many cases they are treated the same as land in general.  As a result, they are widely under-valued and thus mismanaged. 

9)      Similarly, the contribution of species-rich grassland, such as floodplain meadow, is often overlooked.

10)  Restoration of species-rich floodplain meadows at a landscape scale could help in the drive to achieve net zero, support the green economy and provide jobs by extending a regenerative agricultural system that requires no chemical inputs yet recovers well after floods and remains productive during droughts. The animals that graze such meadows and consume the hay require less imported feed, have more varied nutrition and therefore produce healthier meat for human consumption.

11)  Given the policy changes underway as a result of the UK leaving the EU and the UK Government’s commitments to environmental improvements, now is the time to restore floodplain habitats that are both agriculturally productive and rich in wildlife.

Our recommendations

12)  The Committee has a good opportunity to highlight the importance of floodplains and to ensure they are treated as a distinct entity in all land-related policies, such that their value is sustained and used for the good of all.

13)  The Committee should stress the need for floodplains to be future-proofed by promoting an increase in biodiverse floodplain habitats.

14)  The Committee to examine whether the restoration and protection of alluvial soil is prioritised and adequately protected within current mechanisms of funding and policy allowing for a clear pathway for land managers to make appropriate land management decisions

15)  As part of this inquiry into soil health the Committee to question what existing research, programmes and strategies could incorporate a strand of work around alluvial soil.

16)  The Committee to highlight the link between link between the quality of vegetation (i.e., taxonomically and functionally diverse plant communities) and quality of soils, and that vegetation surveys would give a high value indicative data about condition of the soil. Soil biota, which is vital for making top quality soils, develop well only if there is a diverse plant community on the site.

17)  The Committee should champion the role of species-rich grasslands as nature-based solutions that are of equal importance to woodlands and peatlands. For example whilst the Environmental Improvement Plan recognises the role which woodlands play for watercourses, with a promise to continue the “Woodlands for Water” project, to encourage more riparian woodland creation, we are disappointed to see the invisibility of species rich grassland  receiving similar recognition. This despite a number of approaches and conversations with Defra, the Environment Agency and Natural England regarding the tremendous potential for floodplain meadows are water quality, flood management, biodiversity and climate resilience.

18)  Working effectively together, and through strategic plans such as Local Nature Recovery Strategies (LNRS), it is vital to ensure the right habitats are restored on floodplains to tackle soil health. Achieving the optimum balance will require careful planning to avoid conflicts between, for example, food production, government tree-planting targets and flood storage.

19)  Current carbon-offsetting measures (such as afforestation or bioenergy) need to be balanced with biodiversity targets and greater consideration should be given to the carbon-sequestration potential of well-managed soils.

20)  To support farmers in their business decision-making for how they manage their land; there is a role for the mandatory labelling of percentage grass-fed meat and the introduction of a recognised label for meat produced from species-rich grasslands.

21)  To ensure that the forthcoming UK Wetland Inventory, in support of the Ramsar Convention on Wetlands, as highlighted by the Environmental Improvement Plan, include floodplain meadows as a key wetland to be mapped, so underpinning future actions to protect this vital habitat.

22)  As part of the recommendations for how England plans for to improve soil health, there should be a consideration for an overall Floodplain Strategy, allowing for an alignment of different policies and financing, so enabling floodplains to deliver significantly greater public goods. There is currently a gap in this respect, and the Floodplain Meadow Partnership can offer DEFRA and others assistance in drafting guidance. A strategy document should set targets for functioning floodplain habitats. This could be similar to the work on Restoring Meadow, Marsh and Reef (ReMeMaRe) project for Coastal Habitats.   https://ecsa.international/reach/restoring-meadow-marsh-and-reef-rememare 

23)  The Floodplain Strategy should include the following measures:

1. Greater investment into Natural Flood Management measures and reconnecting rivers with floodplains through appropriate policies and funding schemes; e.g. River Basin Management Plans, Catchment Management Plans etc.  Given that 42% of floodplains are no longer connected to their rivers, there is potential for restoring flood storage in the throughout river catchments; 
2. Floodplains included as a specific land-category within the Environmental Land Management Scheme where land-use change (e.g. from arable cultivation to permanent grassland) is often needed to maximise environmental benefits and public goods;
3. Greater recognition of the value of species-rich floodplain meadows;
4. Agricultural advice and support to develop the traditional skills needed to manage floodplains.
5. Spatial targets for the restoration of functional floodplain habitats. Defra to be tasked to work with organisations including the Environment Agency and Natural England to ensure that the ELM scheme (alongside other relevant strategic plans such as Local Nature Recovery Scheme, Nature Recovery Network and Biodiversity Net Gain) contains our recommended spatial targets:

      25% of floodplain area needs to be low input grassland (which equates to almost 200,000 ha) within 25 years – this is based on our knowledge of restoration potential and the scale we believe is necessary for functionality;

      70,000 ha of this area to be species-rich habitat in Favourable Conservation Status - to deliver high-nature-value floodplains and to export nutrients from riverine systems in sufficient quantity to allow natural processes to recover.

Alluvial soil – what makes it special and the challenges it faces

1. The Open University is conducting a range of research projects looking at the impacts of flooding, water regime, climate change and nutrient cycling on floodplain meadows. The outcomes of their research and other recent studies have shown floodplain-meadow soils to hold a significant store of carbon.

2. There is now a clear understanding amongst the general public of the impact that burning fossil fuels has on our climate. But less well known is the release of carbon into the atmosphere from degradation of soils and their above-ground ecosystems.  The IPCC have estimated that 23% of the carbon released into the atmosphere by human activity has come from land-use change.

3. Biogeochemical processes in floodplain ecosystems are very active.  Regular replenishment with sediment during floods enables floodplain soils to accrete material and maintain their fertility. This is in stark contrast to the widespread compaction and erosion found in many lowland agricultural landscapes, from where an estimated 2.9 Mt of soil is lost each year.  The alluvial soils of meadows are particularly important for carbon sequestration because they grow deeper with each flood event.

4. Carbon sequestration and storage in floodplain soils has attracted a range of international researchers. For example on floodplains, deep layers of soil were found to contain large amounts of ‘buried’ carbon (D’Elia et al., 2017). Our own unpublished data suggest that the amount of carbon stored even in the top 10 cm layer of alluvial soil, is very high - further info here; http://www.floodplainmeadows.org.uk/sites/www.floodplainmeadows.org.uk/files/Soil%20Carbon%20stocks%20summary%20130619.pdf .  Investigations into carbon sequestration and storage in floodplain soils under British meadows should therefore be continued (and published). But even without further study, and based on current evidence, we conclude that floodplain meadows should be conserved together with other established grasslands and restored where possible in order to boost carbon-sequestration rates.

5. When comparing the top 10 cm of soil with other habitats, soils beneath floodplain meadows store comparable amounts of carbon to ancient woodland, and while peat stores more near the surface, floodplain meadow soils can go much deeper storing substantial amounts of carbon to a depth of several metres. The roots of many meadow plant species extend up to 3 m into the soil, transferring carbon deeper into the soil profile than arable crops, intensive grasslands or even woodlands. The top 10 cm of soil in a species rich meadow has been measured to have a carbon content of around 13% of its mass, while arable soils typically have a carbon content of just 3%.

6. We are now beginning to see a growing recognition of the value of this habitat within the complex and vulnerable floodplains  – for example in the report Environmental Audit Committee report “ Biodiversity in the UK: bloom or bust?   https://committees.parliament.uk/committee/62/environmental-audit-committee/news/156218/toothless-government-policy-and-targets-insufficient-to-stem-the-tide-of-uk-biodiversity-loss /    one of the recommendations from the EAC regarding climate change are

“Tree planting should not occur on peat soils and floodplains would be better used for restoring floodplain meadows rather than afforestation projects.” 

7. Despite this, in comparison with the focus on peatlands and woodland, species-rich grasslands such as floodplain meadows have not seen the same explicit support in terms of funding programmes and strategies. Their value and contribution to climate change mitigation and adaptation measures, as well as their role in regulating water quality and storage has not been fully recognised within the recently published Environmental Improvement Plan. One consequence of this is that grassland sites with the potential for restoration are vulnerable to inappropriate tree planting or to targeting for the creation of other wetlands types, for which that are neither edaphically or historically suited.

QUESTIONS SET BY THE EFRA COMMITTEE

How can the Government measure progress towards its goal of making all soils sustainably managed by 2030? What are the challenges in gathering data to measure soil health and how can these barriers be overcome?

8. An intrinsic aspect of soil health relates to its structure and pore size.    Soil structure and soil type are critical in determining plant species diversity and in the ability of soil to deliver other benefits such as carbon storage, water storage and food.  Compaction is one of the biggest threats to the soil of a floodplain as wet soils are particularly liable to compaction because they lack strength.   It can alter plant-community composition, as compacted soils become more waterlogged, leading to the development of relatively species-poor inundation communities and invasion by less palatable species such as rushes. Compaction reduces the abundance of soil invertebrates and may impact on soil-surface invertebrates such as beetles and spiders. It can also reduce the ability of a site to store floodwater and re-charge the aquifers below.  Once the structure has been lost through compaction, it can take decades to recover.

9. With their rich root diversity and method of land management floodplain meadows are a vital tool in improving the health of alluvial soils providing plenty of pore space for air and water to move through the soil.  There is a strong link between a quality of vegetation (i.e., taxonomically and functionally diverse plant communities) and quality of soils. Vegetation surveys would give a high value indicative data about condition of the soil.  A key aspect of the Floodplain Meadow Partnership work is around surveying and monitoring the health and diversity of alluvial soils as understanding the soil type, structure and texture will all help in understanding the current species diversity and potential restoration of floodplain meadows. And vice versa.

10. Our own experience and data can help inform how Government might measure progress towards the goal of making soil sustainably managed.   Some soil characteristics, such as the soil profile, texture and structure, can be explored through observation in the field. More detailed information about physical structure requires laboratory analysis of soil samples or more complex field measurements. The Open University have the lab facilities to measure soil density, pore-size distribution and water-retention characteristics – all of which could be used to inform procedure and data. A key challenge in gathering data to measure soil health comes from the actual physical exercise of gathering undisturbed cores and assessing their structure.  It is a time-consuming task and requires skilled technicians. The Open University has well-trained technical staff whom the FMP have access to – skills and teaching which may be useful to overcoming this particular barrier.

11. Another key issue is how soil carbon is measured.  Approaches to carbon accounting and measuring soil organic carbon in grassland soils are usually taken at a depth of 15cm. However, modelling demonstrates that up to 60% of the soil organic carbon is stored at depths between 30-60cm.[i]   This means that measurements can often undervalue the amount of soil organic carbon stored in semi-natural grassland soils, therefore soil carbon measurements should be taken at greater depths.              Initial findings from the soil carbon research by the Floodplain Meadow Partnership on floodplain soil found that the carbon stored in the soils of ancient meadows was about 60% higher than the arable fields.  

Do current regulations ensure that all landowners/land managers maintain and/or improve soil health? If not, how should they be improved?

12. Agri environment schemes have guidance to avoid structural damage and compaction, but the compliance with these measures is not adequately monitored.   Whilst education of landowners to enable them to appreciate maintenance of soil structure is in their own interest is key, however we argue that some monitoring of compliance is still necessary.

13.Another key issue for alluvial soil health are regulations around the protection of watercourses and in particular how buffer strips are used.  The use of buffer strips, which is often advocated for small watercourses, is not appropriate on floodplains, where a larger area is liable to flood. There are numerous studies that have questioned their effectiveness, many of which are reviewed in Prosser et al., 2020 and there is a particularly good recent paper on the subject by Sawartzky and Fahrig (2019). 

14. We think it important that structures put in place for land management, such as the ELM scheme, should recognise the real-world complexity of watercourses and how they interact with terrestrial land.   We suggest a simpler and far more effective means of achieving the scheme’s objectives would be to recognise floodplain as a specific land type, which is readily done using the EA’s own Flood Zone 3 mapping.  This zoning is already available as an overlay for maps to allow farmers/managers/owners to select a suitable option within any new scheme.  The key is for the ELM scheme to adopt the Flood Zone approach and to offer appropriate management options to achieve the potential benefits that floodplains can supply (sediment trapping, nutrient export, pollution control, flood-risk management and biodiversity conservation.)  For example, a buffer strip is of little or no use if maize is being grown on the floodplain in the field behind the buffer.  During a flood event, much of the sediment, nutrients and pollutants would move along the floodplain in parallel to the watercourse until they eventually found their way into the channel.  A buffer strip would offer little or no benefit in these circumstances.  The answer is to eliminate damaging land uses from the floodplain.  To do this the floodplain first needs to be identified as a specific land type.  Not to do so would be a once-in a-generation failure as the opportunity to re-design such a scheme is unlikely to reoccur. 

15.The documented lack of effectiveness of buffer strips strengthens the case for larger scale action to restore functioning floodplains, which are demonstrably effective at storing sediment and processing nutrients.  Whilst we recognise that there is a drive to provide “broad and shallow” options for the Sustainable Farming Initiative ( SFI) to encourage farmers to take them up, we need to avoid using public money to pay for actions which do not deliver.  We therefore argue for the promotion of functioning floodplains on which, even at SFI, the farmer commits to stop the most damaging operations.

16.The FMP’s position is that the protection of watercourses should not rely on narrow buffer strips, but that the river and floodplain should instead be regarded as a holistic system and managed accordingly.  Farmers managing floodplain land (as defined by the Flood Zone 3 map,) should be provided with options to moderate the impact of arable farming (SFI) and then to move to more sustainable land uses through the higher levels available.   An arbitrary width of buffer would result in some land outside of the flood zone receiving public money to be managed in a way that would not achieve the scheme’s objectives.  Better surely to use the existing definition of floodplain to allow the critical areas to be identified and resources targeted to those areas where they can deliver benefits. We would expect the scheme to encourage restoration of grassland across all three ELM levels as grassland offers the greatest benefits in terms of floodplain soil stabilisation, carbon sequestration, sediment trapping, nutrient export and biodiversity conservation.  Similarly the recently extended Catchment Sensitive Farming scheme must also support this approach to managing for alluvial soil health.

17.The critical role soil moisture, and therefore seasonality, plays in soil vulnerability to damage is well understood and it is particularly relevant to floodplains, where the water regime is less predictable.  Managers need to be given flexibility in terms of timing their operations.  It is another reason why floodplain land needs to be recognised and prescriptions tailored to its needs.

Will the standards under Environmental Land Management schemes (ELMs) have sufficient ambition and flexibility to restore soils across different types of agricultural land? What are the threats and opportunities for soil health as ELMs are introduced?

18.There are as yet no targets set for grasslands ( unlike for peat and woodland), no habitat restoration goal for floodplains, nor is there recognition of special measures for alluvial soil. The way we manage our land and support farmers has a fundamental and often adverse impact on the water environment. For example, intensive agriculture, particularly cultivation of maize and other arable crops, contributes significantly to both flood risk and diffuse pollution by increasing run-off, soil/sediment and fertiliser/pesticide loads in rivers. 40% of rivers are currently affected by diffuse pollution from agricultural sources [2]. It has been estimated that poor soil management costs the UK £1.4bn/year in soil erosion, “siltation” of rivers and increased water treatment costs[3]. Supporting and targeting water-friendly farming practices on steep erodible soils and within floodplains would go a long way to reducing chemical-laden run-off and floods whilst enhancing infiltration to replenish aquifers and helping re-build fertile soils that can hold and filter water. Better control is needed over acceptable land uses within the floodplain, for example there should be a presumption against arable and maize cultivation, and a presumption in favour of the restoration of species rich habitats where land use change is critical to protect water and soils.

19.Floodplains should be included as a specific land-category within the Environmental Land Management Scheme where land-use change (e.g. from arable cultivation to permanent pasture) is often needed to maximise environmental benefits and public goods. Groups of farmers with flood-plain land should be encouraged to take up appropriate Sustainable Farming Initiative measures, Local Nature Recovery / Countryside Stewardship plus options, and long-term land use change through the Landscape Recovery scheme.  We would expect to see this measure successfully introduced as a collaborative activity between the Environment Agency, Natural England, Defra, farming group and NGOs. 

20.Floodplains of high nature value that support habitats such as species-rich hay meadows are a vital element of UK natural capital. There is growing recognition of the contribution habitats such as flood-plain meadows can make to both the climate and biodiversity crises, and increasing evidence for the many benefits they provide. A report “Natural Capital of Floodplains” [4] published in 2018 concluded that the overall benefits provided by seasonally inundated flood-plain meadows are greater than those provided by land in intensive agriculture. However there has been a substantial loss of species rich habitats, such as floodplain meadows, through past land-use change.  Nearly 70% of flood-plain land is intensively managed (Heritage and Entwistle 2017[5]) whereas semi-natural habitats such as flower-rich meadows and wet woodland occupy a mere 11%. For example once the dominant land-use on floodplains, species-rich meadows are now small and fragmented, so they are no longer able to provide all those benefits they are capable of delivering (see Appendix 1 for outline of the benefits floodplain meadows can deliver).  

21.An increasing number of projects show how restoration can have many benefits, often at relatively low cost by kick-starting natural processes. We need to see our floodplains as a resource, enabling dynamic natural processes, and working closely with landowners and local communities.  A shift away from arable crops and improved grasslands in floodplains to species-rich meadows (and other linked habitats such as wet woodland and fen) would provide a much more pragmatic and self-sustaining land use that can trap soil running off sloping land, process the nutrients bound to the soil particles, re-build soil fertility and store carbon as well as slowing, storing and filtering the flow of water from the land. These benefits would be realised much more rapidly than if the land were abandoned (e.g. rewilding) or planted up as woodland.

22.At least 42% of rivers are no longer connected to their floodplain, so there is an enormous untapped potential area where increased floodplain storage could be provided. Species-rich floodplain meadows are an extremely cost-effective “no regrets” high nature value farming system that provides multiple benefits, maintaining agricultural productivity whilst helping to meet the ambitions of the 25 Year Environment Plan using Lawton principles (more, bigger, better condition and joined). The partnership sees the restoration/creation of species-rich grasslands as a stepping stone towards achieving more dynamic natural systems. All remaining examples are valuable, but need to be bigger, in better condition and more joined to provide all their potential benefits. Natural England are working (with partners) to develop a new Priority Habitat description 'Floodplain Wetland Mosaic'; this encompasses species-rich meadows and is aimed at recognising the value of natural function and high biodiversity in floodplains.  Again, plans for floodplains will need to include how this freshwater Priority Habitat will be managed and restored.

23.A role the Committee could play would be to advocate the requirement for an overall Floodplain Strategy within the wider Land Use Strategy allowing for an alignment of different policies and financing so enabling floodplains to deliver significantly greater public goods. There is currently a gap in this respect, and the Open University / Floodplain Meadow Partnership can offer DEFRA and others such as the Environment Agency assistance in drafting guidance. As part of this strategy, we propose a number of specific spatial targets for the restoration of functional floodplain habitats and suggest the Committee call on Defra to be tasked to work with organisations including the Environment Agency and Natural England to ensure that the ELM scheme (alongside other relevant strategic plans such as Local Nature Recovery Scheme, Nature Recovery Network and Biodiversity Net Gain) contains spatial targets:

1. 25% of floodplain area needs to be low input grassland (which equates to almost 200,000 ha) within 25 years – this is based on our knowledge of restoration potential and the scale we believe is necessary for functionality 
2. 70,000 ha of this area to be species-rich habitat in Favourable Conservation Status - to deliver high-nature-value floodplains and to export nutrients from riverine systems in sufficient quantity to allow natural processes to recover.

What changes do we need to see in the wider food and agriculture sector to encourage better soil management and how can the Government support this transition?

24.Not only is it important for agri-environment schemes to support delivery of the public goods that a functioning floodplain can provide and to keep stocking density low, there must also be a successful market for the meat products produced.

25.Current food labelling rules on grass-fed meats mean that a product can be labelled as such if only 51% of the livestock feed is grass. This means higher percentage grass-fed products are not distinguished. This also does not distinguish between the quality of grassland habitat used. One may feed cattle entirely on a species-poor grass sward, or on silage made from such a sward, and be labelled the same as cattle fed on a species-rich meadow diet despite this resulting in different nutritional quality of the meat product.  Our recommendation is that there should be mandatory labelling of percentage grass-fed meat and introduction of a recognised label for species-rich pasture-fed meat.

26.The Food Strategy provides an opportunity to shift to shorter, fairer and more resilient food supply chains. The government has committed to publishing a land use framework in 2023 to “ensure we meet our net zero and biodiversity targets, and help our farmers adapt to a changing climate, whilst continuing to produce high quality, affordable produce that supports a healthier diet.” More detail is needed on how this will be implemented and who will be involved in its development. The land use framework will have wide ranging impacts on both market conditions that can support these systems, as well as our ability to meet biodiversity targets.

What does the UK Government need to do to tackle other stressors on soil health such as soil contamination?

27.The management of alluvial soil health through such measures as the restoration of species-rich floodplain grasslands can and should be funded from several sources, including the water industry (where land management changes bring about water quality improvements, reducing treatment costs and potentially helping aquifer recharge), Environment Agency flood risk management budgets, Nutrient management Scheme  ) and, where appropriate, developer-funded biodiversity Net Gain. Working effectively together, and through strategic plans such as Local Nature Recovery Strategies (LNRS), is vital to ensure the right habitats are restored or created in the best places.

Annex 1

A brief history of floodplain-meadow soils

Coarse sediments were widely deposited on floodplains following the end of the last Ice Age around 11,500 years ago. Melting snow fields and ice sheets created swollen rivers each spring that eroded upland areas and re-deposited the transported material onto lowland floodplains. The resultant layers of sand and gravel still underlie many floodplains and are often referred to as ‘terrace’ deposits. These terrace deposits play a pivotal role in the hydrology of floodplains, allowing water to flow freely through them. Estimates suggest that some floodplains have a greater volume of water travelling through subsurface gravels than in the river channel itself. As the winters warmed, the periods of meltwater spate declined in frequency and strength, and the speed of water crossing floodplains became slower. Slow-moving water drops its fine sediment and this forms the basis of alluvial soils. The depth of alluvial soil that has accumulated above terrace deposits on meadow sites can vary from just 15 cm to as much as three metres.

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