We’ve seen what you should do in terms of river restoration in our last post. Now, what shouldn’t you do? What are the things that cause river restoration schemes to fail?
DON’T neglect the three key components: form, process and materials. Intrinsically linked, these three components determine the way rivers work and should be ever-present in your thoughts on river restoration. Do you want shallow sloping river banks to encourage emergent vegetation and berm creation (form), or do you need fast flows and surface roughness to increase aeration and dissolved oxygen content (process)? In both cases you’ll have to think about the type of substrate you’ll need (materials); fine sediment for berm creation and gravel sediment for riffle creation.
DON’T forget it’s about more than just geomorphology. Water chemistry, seed banks, longitudinal connectivity, allocthononous nutrient inputs, diffuse pollution sources and ecological elements such as competition, succession and behaviour will all play a part in determining whether your river restoration scheme is successful.
DON’T apply generic techniques: Every river system is different but more than that every river is different. Initially you have to establish what type of river you’re dealing with: is it groundwater-dominated or runoff-dominated; high-energy or low-energy; alluvial or bedrock? Then you have to get the local story: is the river over-abstracted? Are there surface runoff pressures? Does the river perform a function for society (e.g. flood defence)? The most appropriate techniques for restoration will be effected by these considerations.
DON’T just do what they did: The River Restoration Centre in the UK and the EU RESTORE website contain many good case studies of effective river restoration works. However, and as the disclaimer often says, ‘these techniques were developed to suit site specific criteria and may not apply to other locations’. There is no such thing as one size fits all in river restoration, and simply doing exactly what someone else did may have unexpected consequences.
DON’T take unnecessary risks: The River Cole near Swindon and the River Skerne in County Durham have been used as demonstration sites for a range of different restoration techniques. Some things have worked and some things haven’t, but no unnecessary risks have been taken. You would not test the techniques tested here at a SSSI or on a heavily urbanised floodplain. Particular care should be taken in high-energy rivers where system response can be dramatic and unpredictable, and also in low-energy systems where relic features may be inadvertently lost through mismanagement and rivers do not possess the power to reassert their form.
DON’T do nothing: It can be a bit daunting if you’re a landowner or conservation trust and you want to improve your river. There are several forms to fill out, including applications for flood defence consent, and you’ll need to write up a report as well as perhaps completing an environmental impact assessment or a water framework directive assessment. It’s often best to ask a consultant to do this but whatever you do, don’t do nothing! We all have a responsibility to undo the damage done by previous generations and ensure our children have a decent world to inherit. Plus, I imagine you get a very special feeling when you go back to a site that looked pretty iffy five years ago and it’s all lovely because you helped restore it.
As in the previous post, this list isn’t exhaustive. Perhaps you know of something else that’s an absolute no-no when it comes to river restoration?