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Showing posts with label land management. Show all posts
Showing posts with label land management. Show all posts
Sunday, 12 December 2010
Thursday, 9 December 2010
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.
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.
Saturday, 9 January 2010
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.
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.
Friday, 30 October 2009
PINPOINT
Just leaving Cornwall after a week learning how to identify and tackle diffuse pollution of rivers using the PINPOINT method. Its the end of October and the weather has been impresive, hitting 18 to 20 degrees most days. Three of my fellow students spent their mornings swimming off the North coast. It wasn't for me, as much for the 5am starts as anything.
The course was run by the West Country Rivers Trust and the Association of Rivers Trusts. We were given a great insight into the work the West Country Rivers Trust have carried out down in Cornwall and Devon on finding win-win situations with landowners and farmers to reduce inputs of sediments and nutrients to rivers. This improves in-stream habitats and increases Salmon and Trout numbers. It also creates a deeper understanding between farming and conservation creating less polarised views.
It was good to see a variety of farms from high intensity dairy operations to low input extensive organic smallholdings. The contrast between the two was fascinating. We saw how dairy operations can concentrate nutrients over a small area of land whilst more extensive systems gave us a view into a nearly lost pastoral English landscape that provides a true habitat mosaic. What was even more intriguing was the mix of options between the two systems that helped tackle diffuse pollution. Simple measures such as fencing river banks, putting hard coverings around supplementary feeders, sub-soiling to reduce soil compaction and coppicing multi-stem river bank trees to reduce shading and increase ground cover all enhance riparian habitats and break the links between erosion sources and watercourses.
Its now the turn of myself and my fellow students and rivers trusts colleagues to roll out similar schemes around the country. Its only by working with agricultural communities that we will find ways to reduce diffuse pollution without impacting on farm incomes. Many of the options available will even save time and money.
The course was run by the West Country Rivers Trust and the Association of Rivers Trusts. We were given a great insight into the work the West Country Rivers Trust have carried out down in Cornwall and Devon on finding win-win situations with landowners and farmers to reduce inputs of sediments and nutrients to rivers. This improves in-stream habitats and increases Salmon and Trout numbers. It also creates a deeper understanding between farming and conservation creating less polarised views.
It was good to see a variety of farms from high intensity dairy operations to low input extensive organic smallholdings. The contrast between the two was fascinating. We saw how dairy operations can concentrate nutrients over a small area of land whilst more extensive systems gave us a view into a nearly lost pastoral English landscape that provides a true habitat mosaic. What was even more intriguing was the mix of options between the two systems that helped tackle diffuse pollution. Simple measures such as fencing river banks, putting hard coverings around supplementary feeders, sub-soiling to reduce soil compaction and coppicing multi-stem river bank trees to reduce shading and increase ground cover all enhance riparian habitats and break the links between erosion sources and watercourses.
Its now the turn of myself and my fellow students and rivers trusts colleagues to roll out similar schemes around the country. Its only by working with agricultural communities that we will find ways to reduce diffuse pollution without impacting on farm incomes. Many of the options available will even save time and money.
Sunday, 18 October 2009
The rivers are quiet.
I keep getting reports of fish movement upstream but I haven’t had the luck to spot anything yet. Since the records came in the rivers have dropped again. Even though there’s been a day of rain it has only just made the dizzy heights of light drizzle and the river is stubbornly refusing to respond. I went down to Aysgarth Falls late afternoon on Sunday but the water was so low nothing would have made the attempt. A heron and a few mallard ducks sat above the upper falls and that was about all. The electro-fishing kit is in store for the year and my sampling nets are only going to get another day or so. Things in the rivers seem quiet and there is just the spawning to come and then it will be a matter of waiting for spring before I can start serious river surveys again.
Plenty to do in the meantime so boredom won’t be a factor. Down to Cornwall next week to learn about a farm survey method called PINPOINT that the river trusts and Natural England have organised. This aims to help identify where the sources of diffuse pollution on a farm are. It should help farmers meet the requirements of the Water Framework Directive, may even save some money. Then there are lots of farm surveys to carry out before I take three weeks leave. The plan is to lock myself away on Islay and get on with writing up the project I’ve been working on for the past three years. I’m hoping it will be miserable forcing me to sit in and get on with it...it would be just my luck for unseasonal sun!
Plenty to do in the meantime so boredom won’t be a factor. Down to Cornwall next week to learn about a farm survey method called PINPOINT that the river trusts and Natural England have organised. This aims to help identify where the sources of diffuse pollution on a farm are. It should help farmers meet the requirements of the Water Framework Directive, may even save some money. Then there are lots of farm surveys to carry out before I take three weeks leave. The plan is to lock myself away on Islay and get on with writing up the project I’ve been working on for the past three years. I’m hoping it will be miserable forcing me to sit in and get on with it...it would be just my luck for unseasonal sun!
Sunday, 11 October 2009
Change and restoration
Upland rivers are fascinating places that possess a raw quality. Full of rapid change, violent spates to low flows in quick time, they pose challenges to people and nature. It is this rapidity of change that keeps them alive, keeps people drawn to them and puts their ecosystems on a knife edge of existence. One severe flood, drought, landslip or pollution event can alter their ecology for years. And when a natural system flips between threshold states dragging it back to its original condition is complex and challenging, beset with frustrating feedbacks and full of unexpected consequences. The new science of restoration ecology has discovered this time and again. What has appeared to be an obvious intervention can force a natural system to skew off towards some other state not accounted for during intervention planning. This has resulted in more measured approaches to reverse interference and has revealed that ecology does not exist in easily flipped parallel states but occurs in complex dimensions of interacting multivariate factors that we can never fully understand.
But not fully understanding something does not mean that we cannot understand it enough. Beneath the aesthetics of these places lie scale upon scale of interacting processes within and between both the living and non-living components of a system that create forever fluctuating conditions. However, even though they fluctuate, under prevailing conditions they are always pulled back towards some unknown average. In order to understand enough we need to simplify these interactions down to basic assumptions that explain them in as much detail that is required in order to predict the outcome of an intervention. This is not a magical process and can only come from experimentation both in laboratories and natural systems. And we are beginning to understand enough though it would be arrogant to suggest that we will never make mistakes during restoration efforts, but with restoration ecology it is the mistakes that guide learning.
The biggest experiment (and probably mistake) we are undertaking is one we have not planned but has come as a consequence of modern economies and lifestyles. An article published in 2007 in Global Change Biology by Durance and Ormerord showed that upland stream macro-invertebrate assemblages may decline by 21% for every degree centigrade rise in water temperature. This is of concern to freshwater ecologists as after primary production these are the most important components of upland river systems. What we have learned in recent years is that such a change would be difficult to reverse and as future temperatures are forecast to increase for sometime it may be that these upland river systems are destined to become shadows of their present selves.
But not fully understanding something does not mean that we cannot understand it enough. Beneath the aesthetics of these places lie scale upon scale of interacting processes within and between both the living and non-living components of a system that create forever fluctuating conditions. However, even though they fluctuate, under prevailing conditions they are always pulled back towards some unknown average. In order to understand enough we need to simplify these interactions down to basic assumptions that explain them in as much detail that is required in order to predict the outcome of an intervention. This is not a magical process and can only come from experimentation both in laboratories and natural systems. And we are beginning to understand enough though it would be arrogant to suggest that we will never make mistakes during restoration efforts, but with restoration ecology it is the mistakes that guide learning.
The biggest experiment (and probably mistake) we are undertaking is one we have not planned but has come as a consequence of modern economies and lifestyles. An article published in 2007 in Global Change Biology by Durance and Ormerord showed that upland stream macro-invertebrate assemblages may decline by 21% for every degree centigrade rise in water temperature. This is of concern to freshwater ecologists as after primary production these are the most important components of upland river systems. What we have learned in recent years is that such a change would be difficult to reverse and as future temperatures are forecast to increase for sometime it may be that these upland river systems are destined to become shadows of their present selves.
Friday, 9 October 2009
Modelling at the catchment scale
Understanding how water moves across the land and what chemicals and sediments it delivers to rivers is vital to the understanding of river ecology. The rivers trust movement has played a key role in recent years by helping to decipher how catchment processes control river morphology and how morphology and water quality affect ecology.Excessive fine sediment in upland rivers degrades river habitats by clogging up the spaces between the gravel. This reduces egg survival of Salmon and Trout and changes the macroinvertebrate communities by favouring organisms such as Chironimidae worms over Stonefly and Mayfly.
A number of rivers trusts including the Yorkshire Dales Rivers Trust have been using a modelling tool developed by Durham and Lancaster universities called SCIMAP (Sensitive Catchment Integrated Modelling and Analysis Platform). This provides detail on where fine sediment is likely to be delivered to a watercourse based on slope, landcover and its associated erosion risk and rainfall.
SCIMAP outputs show the average risk for in-stream fine sediment in any catchment being modelled with a number of risk classes either side of the average rangi
ng from high risk (red) to low risk (green). Underneath this output is a second output in grey that highlights the land parcels of a catchment most likely to be the source of the sediment. From this it is easy to locate the red 'streams' and then look up stream for the most likely locations that are delivering the sediment. Some ground truthing is then necessary but once the risk has been established it is possible to enter negotiations for changing land management to methods that can reduce these inputs. Simple measures such as buffer strips or contour planting of trees slows surface run off allowing sediment to settle out before the water reaches a watercourse.This has the benefit of reducing the degradation of rivers and streams and allows species composition to restore itself back to the natural community of the river type. It is these simple habitat measures, developed through catchment scale thinking, that will restore habitats to something like their potential. This kind of large scale thinking is constantly developing which makes working as part of a rivers trust an exciting and rewarding vocation.
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