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Willow Spiling To Protect Farmland

Bank erosion of streams pollutes watercourses with fine sediments and phosphates that can disturb the local ecology. It also removes sections of the farm to be deposited downstream, either within the river or on someone else’s land when the river overtops it’s banks. There are numerous methods for controlling this process and so reduce the rate at which soils are lost to rivers. The obvious method is fencing the watercourse to remove stock from the bank side. This allows vegetation to flourish creating a strong root stock that binds soils together. But sometimes just fencing the river bank is inadequate as erosion has taken hold and every flood pulse takes another section of bank and then the watercourse begins to eat into fields.

More drastic hard engineering methods can solve this. Gabion baskets for example create a strong buffer between fields and water. Such methods can be successful but they operate against natural processes and so always look at odds with the landscape. Moreover they too can wash out adding an extra ugliness as they hang into the river spilling their gravel back to the water.

There are intermediate methods that are successful and work with the natural features of a river. Matt Neale, the local ranger for upper Wensleydale, has championed willow spiling to protect banks, and fields, from erosion. This method seems to do the trick on most occasions and adds habitat to the river providing refuge and shade for fish, birds and mammals such as otters. Having visited sites where the Eden Rivers Trust had successfully employed the method Matt identified sections of the Ure that would benefit from this method. The first place he trialed willow spiling was on the river Ure just below Hawes. Here the river was eating into the bank and soil was being lost rapidly from the farm with every high flow event.

The method is simple but effective. Stakes are driven into the river bed close to the bank, spaced at two or three metre intervals. Live willow rods are then woven between the stakes to provide a permeable barrier between the river and the bank. This helps to reduce stream power and thus erosion and it also slows the water enough to allow sediments to drop out behind the willow spiling. The bank then builds up as new sediment is deposited whenever the river overtops the willows. The added benefit with using willow rods is that they take root and flourish in these locations. The roots further bind the soil whilst the new tree growth slows the water down even further and more matter is deposited until the bank becomes completely revegetated. The habitat created by this is valuable and helps to protect farmland creating one of those rare win-win situations.

Since the first trial Matt has carried out the method on several other sections of the river Ure and Duerley Beck. He has refined the process and now builds up coarse gravel behind the spiling to encourage fine sediments to deposit out offering further protection to the willow rods whilst they take root. When possible soil is packed into the coarse sediments providing a substrate for the growth of bank side vegetation, again this further binds the bank providing a more stable environment which offers improved chances that the work will be successful. When it is appropriate the bank is reprofiled to create a less vulnerable slope.

All of the sites that Matt has worked on have been succesful with one exception. This is at a location where a large glacial deposit, possibly a recessional moraine, is eroding badly. The land slip is substantial and the processes causing the slip are not simply undercutting of the bank by the river since the slope has become unstable. These glacial desposits are unconsolidated, porous and permeable meaning that water seeps through them providing a good medium for failure points to emerge. Where the processes causing erosion have been caused by river water the method has been extremely succesful and the habitat created appears natural and undisturbed.

Soil Compaction

Many meadows and pastures suffer soil compaction due to the regular passing of heavy machinery and high stocking rates. This can increase run-off during rainfall events and result in the delivery of fine sediments and nutrients to watercourses that can have significant impacts on river ecology. Soil compaction also has impacts on farm yields. If compaction impedes the root stock from penetrating into the soil layers then plant growth, and nutrient uptake, is reduced. This can result in poor crops of silage and hay which are required for feeding stock through the winter months; which is especially important in upland locations where growing seasons are short and winters long.

There are methods to improve conditions where soil compaction has occured. Sub-soil ploughs can penetrate below the compacted layer and break the soil allowing root penetration. This is not always possible in upland regions where soils can be thin with bedrock and boulders close to the surface. Steep slopes can also hinder the use of sub-soil ploughs. Aerators are often a better solution in such locations. These simple rotary blades penetrate into the soil and through the compacted layer allowing greater yields due to oxygen replensihment of the soil and root growth beyond the compacted layer.

If this is carried out in conjunction with newer methods of slurry spreading then yields can be massively improved. Two methods that appear to improve nutrient uptake are dribble bars and slurry injectors. These reduce the liklihood of run-off and allow improved use of a nutrient resource. If carried out alongside aerators and soil testing, for nutrient levels and pH, then savings in time and money can be passed onto the farm enterprise. Often pH levels can be lower then optimal and testing can identify where lime is required. This raises the pH and improves plant nutrient uptake. Soil testing can also idnetify which fields have high levels of phosphates and so allows the farmer to reduce inputs saving them money on fertiliser purchase.

These kind of options, if built into the farm plan, can be beneficial to the farmer and help improve the ecological condition of rivers. Cost of the machinery can be prohibitive but presently there are grants that can help with purchasing the kit. For example Yorkshire Forward's Farm Resource Efficiency Programme grants (FREP: www.yorkshire-forward.com/helping-businesses/rural-businesses/funding/frep) will pay up to 60% of costs. It will even pay up to 50% of costs for the pruchase of one piece of kit for contractors. These grants can make such options feasible for the farmer, either to purchase the kit directly or through their contractors.

Hay time



Soil profiles can help identify if compaction has occurred



Slurry injector





Dribble bar on umbilical

Species found in the dales rivers

Some of the species found in the upland rivers of the Yorkshire Dales.

Brown Trout



Brown Trout Fry



Bullhead





Stone Loach





White Clawed Crayfish





Cased Caddis Fly



Minnows

Fish passes

Many of the Yorkshire rivers have endured an industrial past that reduced their biological diversity. There are stories that during the industrial revolution the Aire was so heavily polluted on its course through Leeds that it's surface could be set on fire. Thankfully recent years has seen a more enlightened attitude and our rivers have see steady improvements, with some unhelpful dips after pollution events. There are still historic headaches that river managers have to tackle. All the Yorkshire rivers are dotted with weirs built to service the old mills. Whilst these have become a part of the aesthetic nature of riverscapes they pose problems for migratory species including lamprey, eels, salmon and trout that have to navigate their way upstream against barrier after barrier that impedes their rout. In low flows the fish can become trapped behind the smaller weirs. In some locations on the Wharfe, such as at Otley, the weirs effectively stop upstream migration of fish and have drastically altered the food webs of the upstream river system.



The Yorkshire Dales Rivers Trust have recently worked in partnership with the Environment Agency to develop a fish pass with photographic recording equipment at Boston Spa, on the river Wharfe. The pass is now up and running and it is hoped it will enable safe upstream migration for salmon, trout, eels and lamprey. The camera equipment will record each fish that navigates the pass to supply important data on fish movement. Ideally we would aim to provide all the significant unnatural barriers with similar passes but the cost is prohibitive so development of fish passes has to be very selective. In the meantime each fish pass is one more battle won to help improve the river ecosystem.

summer sun

The rivers are very low after the long spell of dry weather. Askrigg and Newbiggin Becks are completely dry in sections and upstream of Worton the main Ure is turning green with algae. These periods of low flow, coupled with algal blooms, create seasonal bottlenecks that limit populations of fish and flylife. Algae can soak up the dissolved oxygen during the night, as plants switch from photosynthesis to respiration. During the early hours the river can become depleted of oxygen to the extent that severe fish kills occur. When the algae dies back it smothers gravel habitat and depletes oxygen as it decomposes through microbial action.

Under natural conditions upland rivers would be oligotrophic, or low nutrient, relying on seasonal inputs of leaf litter and dying salmon after spawning. But in urbanised and agriculutral catchments these dynamics are changed through the inputs of human-derived nutrients. It doesn't take much phosphate to lead to eutrophication (the change from a lower to higher nutrient status). When this occurs the ecology of the river changes too. This can be through reduced populations of typical species or invasions of species pre-disposed to survive under the emerging conditions. In dales rivers populations of fish, including salmon and trout, are lower then expected suggesting issues of pollution. But barriers, such as weirs, also limit their populations showing that impacts on rivers are multiple.

At one time pockets of de-oxygenated water moved with the tide along the Humber estuary stopping upstream migration of spawning salmon and trout, and downstream migration of smolts (salmon and trout that undergo physiological changes enabling them to live in saltwater). With more stringent regulations on industry, and the decline of the UKs indutrial base, this has been reversed and migrating fish stand a chance of reaching their spawning grounds. The rivers trust is trying to improve the habitat of these upland rivers to ensure that spawning streams are able to support populations of salmon and trout fry. Providing shade to river banks through tree planting, preventing cattle and sheep accessing rivers and adding structure to stream habitats (for example through the inclusion of large woody debris) all offer habitat for salmon and trount young.

River restoration

This is an exciting time to be involved in river ecology. Not only is river restoration becoming more research focused but the river itself is now seen as a system directly connected to landscapes by numerous processes and feedbacks. These riverscapes are constantly interacting with landscapes through hydrological connectivity and interspecies relationships meaning that the river is an integral component of the wider ecology of a catchment. More than this the morphology, ecology and quality of a river is governed by processes that work at catchment scales. For example in the headwaters of a stream it is the hydrological flow paths emerging at the upper reaches of the landscape that govern instream flow rates, discharge, sediment and nutrient delivery, river morphology and finally in-stream ecosystems.

In the past this lack of spatial context has often resulted in restoration that fails due to rivers not being viewed as am emergent response of the catchment. Tackling eroding river banks is a case in point. Management and restoration has often focused on the immediate surroundings of the issue, such as putting in place buffer strips, shoring up or reprofiling the bank. This is despite eroding banks being a symptom of upstream processes such as soil compaction, drainage or deforestation which all increase the speed at which water reaches the channel network and thus the erosive power of a river.

Now that these connections are being made river restoration is becoming process orientated and thus more likely to be succesful. Whilst this is exciting it also poses numerous difficulties. One such issue is that working on one location can result in the need to work with multiple land owners (as the focus shifts to upstream processes) some of whom are more receptive then others. This requires skills that go beyond knowledge of river systems into social science and negotiation and may require teams of multi-disciplinary practitioners in order to develop plans and inform land managers. Where such teams are in place river restoration is becoming more succesful and populations of indicator species such as salmon and trout are becoming re-established.

Winter in the Yorkshire Dales

Winter has hit the dales in a way it hasnt for decades. The riverscapes are surrounded in white that glistens in the low winter sun. Sheep huddle together behind walls waiting for deliveries of food that arrives by tractor which, despite their traction, also slip across the surface. The rivers are running low as all the precipitation is stored in snow and ice, the freezing nights keeping water locked up.

Cars have deep coverings of snow and roads look like gorges as the ploughs scrape them free of snow leaving steep edges on either side. The forecast suggests we have at least two more weeks of this and with drifts already reaching above head height the next days promise impresive sights.



The thaw is held up by the sub zero temperatures dipping to -8 in the dales and colder still the further north one travels. When this huge store of water eventually flows the rivers are set to rise substantially. The worst case scenario for those living in towns downstream of here is a rapid temperature rise coupled with rain. Such conditions will undoubtedly lead to flooding, and misery, for many.

Research into land management suggests that compacted soils and extensive drainage exacerbates flooding by shifting water rapidly from land to river resulting in sharp spikes in the hydrograph. The key to the next few years, as we move towards the prescriptions of the EU Water Framework Directive, is to understand how land management effects water and more importantly identify methods for improving conditions whilst making sure upland farmers do not lose income. This is an exciting time for freshwater ecology as local scale perspectives are stretched to the catchment scale which provides many of the controlling factors on river ecology and quality.

The incredible thing is that the whole country is white, smothered in deep drifts and layers of weeks of snow. Satelite photos from NASA display this strange image of the UK. It looks like not only Yorkshire rivers are at risk. In the meantime the landscape looks fantastic and we all hope the thaw occurs in a slow, steady manner.