Fields & Forests

“The high ground feeds the lowlands.” In rural landscapes, rainwater should linger, soaking into healthy soil, replenishing groundwater, nourishing roots along the way. Under natural conditions, upland forests and wetlands act like sponges and speed bumps, slowing the journey of water to the valleys. Unfortunately, modern farming and land management have often done the opposite. Compacted fields, straightened ditches, and deforested slopes send runoff rushing downslope fast and dirty, carrying soil and pollutants with it. This creates a cascade of problems: erosion strips fertile topsoil, rivers become choked with sediment, and downstream areas face higher flood peaks and poorer water quality. Below, we explore how intensive farming practices and engineered river modifications have altered the water cycle, and how working with nature can help slow the flow. (We will introduce Natural Flood Management (NFM) here as a solution, to be detailed on another page.)

Intensive Farming and Bare, Compacted Soil

Over the past several decades, agricultural intensification has dramatically changed the countryside. Fields have become larger and more uniform, heavy machinery regularly pounds the ground, and hedgerows or field margins have been removed to maximize arable land. These “improvements” have come at a cost to soil structure and permeability. Compacted soils caused by repeated ploughing and heavy tractors do not absorb water well; rain runs off instead of infiltrating. In fact, poorly managed, compacted soils don’t allow drainage, increasing surface runoff and watercourse pollution, whereas well-managed soil can slow the flow of water off farmland. This means that when storms hit, more water and more mud wash straight into ditches and streams rather than gently soaking into the earth.

Another major issue is the lack of vegetative cover in winter. Modern crop rotations often leave fields bare after harvest – gone are the days of routine fallows, set-aside fields, or winter cover crops. Exposed bare soil in the rainy season is extremely vulnerable to erosion. Heavy rain can dislodge soil particles and create rivulets that carry off the fertile topsoil. In the UK an estimated 2.2 million tonnes of topsoil are eroded each year, and around 70% of the sediment that ends up in rivers is from agriculture. Not only does this rob farms of nutrients and organic matter, it clogs waterways and raises water treatment costs downstream. Studies confirm that simply keeping fields green through winter makes a huge difference – planting cover crops (instead of leaving soil bare) helps limit surface runoff that leads to flooding and soil erosion. A recent UK assessment of regenerative farming found that minimizing bare soil (for example, by using winter cover crops) was the single most beneficial practice for soil health, greatly reducing erosion and runoff while boosting biodiversity. Likewise, avoiding excessive tillage and timing field operations carefully can prevent unnecessary soil compaction and runoff.

Intensive farming has also meant fewer natural buffers in the landscape. Hedgerows and shelterbelts that once bordered fields have been lost in many areas. Those hedges, however, are unsung heroes of water management. A dense hedgerow acts like a mini-dam and filter on the hillside: it intercepts raindrops so they hit the ground with less force, and it slows the flow of water moving across the surface, giving more time for infiltration. By the time water trickles through a hedge line, much of the silt has settled out behind the vegetation instead of being carried off. The deep roots of hedgerow trees and shrubs also break up the soil and create channels for water, helping it penetrate deeper and reducing surface runoff. In contrast, crops or grasses alone have shallower roots and can’t match this water, absorbing power. Reintroducing hedgerows, grassy strips, or woodland belts on farms is therefore a key step to slow runoff and trap sediment. It’s a win-win: studies show integrating trees into fields (agroforestry) can reduce flood risks and protect water quality while also benefitting farm productivity.

In summary, modern agricultural practices that leave soil compacted or bare have made it much harder for rainwater to soak in. The result is more flashy runoff, muddy water speeding off fields, which contributes to local flooding and sends farm nutrients (like nitrogen and phosphorus) into watercourses. These nutrients and sediments degrade river health, causing algae blooms and harming aquatic life. Reversing these trends will require a return to better soil stewardship: keeping soils covered, giving fields an occasional rest, using lighter machinery or controlled traffic to avoid compaction, and bringing back natural landscape features (trees, hedges, buffer strips) that help rain soak in where it falls.

It is important, however, not to lay blame solely on farmers. They have come under increasing pressure to boost productivity as we demand cheap food and supermarkets relentlessly drive down prices. Many farmers are caught between economic necessity and environmental responsibility, often forced into practices that harm the landscape simply to survive financially and to keep food on our tables.

Straightened Streams and Rapid Drainage

Not only have our fields changed, but so have our rivers and streams. For centuries, people have tried to tame rivers to protect farmland, digging ditches, straightening streams, dredging channels, and installing weirs or small dams. The intention was to whisk water away quickly, preventing it from flooding fields. In the UK, this legacy is very apparent: about 97% of rivers are fragmented by artificial barriers like weirs – averaging one barrier every 1.5 km of stream, and many watercourses have been “canalised” (trained into straight ditches). Unfortunately, removing a river’s natural bends and pools doesn’t eliminate floods; it often makes things worse. By stripping out meanders and bankside vegetation, we’ve created channels that move water faster but at a cost: straight, smooth rivers send a surge of water downstream that can overwhelm capacity and cause flooding. As one expert explains, if a river is kept straight, water will “fly” through the system; the speed and accumulating volume means that eventually “there’s no capacity to hold the water and flooding occurs” downstream.

Natural rivers are sinuous and rough, with curves, pools, woody debris, and floodplain marshes that act like speed bumps. When those features are engineered away, several negative impacts follow. First, flood peaks amplify, flood waves travel faster and hit downstream communities with less warning and higher water levels. Straightened channels effectively shoot water like a cannon into towns that lie below. Second, water quality and habitats suffer. A straight, fast-flowing drain tends to pick up and carry more sediment because the flow has more energy. Historically, towns and reservoirs downstream of heavily drained farmland have received murky, silt-laden water after storms. Aquatic creatures also struggle in such uniform channels, there’s less shelter for fish and the swift current can scour away spawning gravels. Indeed, it’s now recognised that removing a river’s natural meanders has degraded aquatic habitats and water quality while heightening flood risk. In other words, the old approach of “river straightening” achieved the opposite of its intent.

Engineered structures like weirs and small dams, installed for mills or irrigation in years past, contribute to these problems as well. They segment the river, slowing flow in some parts but creating backups in others, and prevent fish from moving freely. Many weirs are in locations that no longer serve a useful purpose, yet continue to disrupt the natural flow regime. By holding water back artificially or diverting it into concrete channels, these structures have altered how rivers respond to heavy rain, often pushing the flooding problem further downstream rather than truly solving it.

The cumulative effect of all these modifications – rapid field drainage, straighter channels, and frequent barriers, is a river system that delivers water downhill far too efficiently. As a European environmental review noted, flood waves today are higher and move faster than in the past, precisely because our straightened rivers and drainage networks rush water off the landscape so quickly. Combine that with more extreme rainfall events due to climate change, and it’s a recipe for “fast and dirty” floods. Our ancestors wanted to keep water off the land, but now we see that making water race through the landscape causes downstream harm and degrades the rivers themselves. So, what’s the alternative? The emerging answer is to restore a bit of the rivers’ natural wiggle and breathing space.

Rewilding Wetlands and Woodlands to Slow the Flow

If the problem is that water is leaving the highlands too quickly, one solution is to make it linger longer in the uplands and mid-catchment. This is where fields and forests can work together to our benefit. Healthy forests, wetlands, and well-managed farmlands all have tremendous capacity to absorb and slow down water. Research has famously quantified this: an acre of parking lot produces as much runoff as 36 acres of forest under the same rainfall. In other words, natural ecosystems like woodlands have a sponge-like effect, trees intercept rain with their leaves, the spongy forest floor (leaf litter and organic soil) soaks up water, and root networks create porous soil that infiltrates water deeply. Deforestation, conversely, eliminates these buffers: without trees, more rainwater becomes immediate runoff, leading to higher flood peaks and more erosion. This is especially critical on hillsides. Reforesting even some “sub-prime” agricultural lands on slopes can significantly slow floodwaters heading for the valleys, as the vegetation and soil in woodlands act as natural flood control infrastructure.

Wetlands are another key ally. Wetland areas, whether upland bogs, wet meadows, or floodplain marshes, function as natural reservoirs. When heavy rains come, wetlands spread out and hold excess water, then release it slowly over time. Draining wetlands for agriculture or development has removed these natural holding basins. Moreover, many wetlands (particularly peatlands) are incredible carbon stores. Peat soils build up over centuries as waterlogged conditions preserve organic carbon. When we drain peatlands for farming (as was done in peat bogs and fens), that stored carbon begins to oxidize and escape to the atmosphere. Re-wetting and restoring such wetlands yields a double benefit: it revives the land’s ability to store water and keeps vast amounts of carbon locked away. In fact, peatland wetlands cover only ~3% of the Earth’s surface but store more than twice as much carbon as all the world’s forests. Letting these areas stay wet (or re-wetting them after years of drainage) is now seen as a crucial climate strategy, preventing millions of tons of carbon release, while also reducing downstream flood risk and improving water quality. For example, projects in the UK and abroad that re-flood drained peat fields have shown decreased flood flows and cleaner water leaving those areas, as water slows down and sediments/nutrients are filtered out in the wetland.

Bringing woodlands and wetlands back into the landscape does not mean abandoning farming, it means balancing it with natural infrastructure. Strategic planting of trees (e.g. woodland on steep slopes, riparian buffers along streams, or shelterbelts around fields) can intercept overland flow and stabilise soil. One report notes that adding strips of woodland in agricultural catchments helps reduce runoff and pollution, while even benefiting the farm by sheltering crops/livestock and improving soil over time. Similarly, restoring or creating small farm wetlands or ponds in low-lying field corners can catch muddy water before it enters a stream, allowing sediment to settle and water to percolate. These nature-based measures store water higher in the catchment during storms, thereby lowering the flood peaks downstream and keeping rivers clearer. Indeed, after one river in Cumbria (Swindale Beck) was returned to a more natural, meandering course with wetland features, local observers noted the river “cleaned itself”, the slower flow now drops sediment on the floodplain instead of sending murky water to a distant reservoir. Fish and wildlife quickly returned as well, showing the ecological benefits of such restoration.

It’s important to highlight that these interventions are not one-size-fits-all; every farm and catchment is different. But the general principle is universal: landscapes with more vegetation cover, healthier soils, and restored natural water storage will produce gentler runoff. Rainwater is given opportunities to pause and soak in; in field soil, in wooded hills, in bogs and ponds, rather than immediately surging into a flood torrent. By holding back water and sediments, upstream fields and forests act as natural safeguards for those living downstream.

Introducing Natural Flood Management (NFM)

The shift in thinking described above is often termed Natural Flood Management. NFM is an approach that works with natural processes across a whole catchment to reduce flood risk and improve water quality. Instead of just building higher flood walls downstream, NFM asks: how can we slow, store, and filter the water in the landscape before it becomes a flood? This can involve many techniques, restoring river meanders, planting woodlands, installing “leaky” dams of wood in streams, reconnecting rivers with their floodplains, re-wetting bogs, creating buffer strips and ponds, and so on. The common thread is using nature’s own tools to store and slow the flow of water through a catchment. For example, a fallen tree or a beaver dam in a stream will hold back water temporarily, releasing it gradually and preventing a sudden flood peak. Vegetated areas will absorb runoff like a sponge, and rough, winding streams will dissipate energy so that downstream areas see a lower, delayed surge.

Natural Flood Management is gaining momentum as a complement to traditional engineering. It recognises that purely “grey” infrastructure (concrete channels, levees, culverts) has limitations and unintended consequences. By reintroducing green infrastructure upstream, we can take pressure off downstream defenses. Importantly, NFM also delivers side benefits: cleaner water (since sediments and pollutants are filtered out by soil and vegetation) and richer habitats for wildlife. When done thoughtfully, it can even enhance farm productivity (through improved soil health and shelter) or provide new income streams (like payments for ecosystem services, or sustainable forestry products from woodlands).

In this Fields & Forests context, NFM is about recognising that farms and forests are not just producers of food or timber, they are also crucial water managers. If we reward and support landowners for keeping their soils in good condition and maintaining landscape features that hold water, we all benefit. As the Royal Society emphatically put it, soil and land management should take centre stage because well-structured soils and restored ecosystems are natural flood infrastructure. There is growing evidence that investing in better soil practices and habitat restoration upstream can significantly reduce flood risks downstream while also meeting climate and biodiversity goals.

We will delve deeper into specific Natural Flood Management measures elsewhere on Slow The Flow. For now, the key takeaway is that the current problems of rapid runoff and polluted rivers in rural areas are not inevitable. They result from choices in how we’ve managed fields and forests, and by making different choices, we can change the outcome. With cover crops and healthy soils, rain can sink into fields instead of skating off. With wetlands and woodlands revived, the landscape can buffer and cleanse the water that flows through it. The high ground will always feed the lowlands with water, but it’s up to us to decide whether that feed is a destructive gush or a gentle, life-giving flow.