If the purpose is to provide a home for ‘large woody debris and leaky dams’ these would have to be managed very carefully if new problems are to be avoided. Indeed, I doubt whether this measure would be acceptable in many locations, for three reasons: First, man-made dams have to be constructed to extremely high standards because the risk caused by a failure is unacceptable. Whilst natural ‘leaky dams’ would clearly be on a small scale, the risk of failure, and in particular a ‘domino’ flood wave, would have to be very carefully considered. Second, one of the greatest causes of property flooding is the blockage of bridges by woody debris. Third, storing water behind dams, even if secure, will raise water levels upstream and therefore increase the area of floodplain. Surrounding landowners would have to accept this. And… even beavers lose their homes in severe floods!
Whilst perhaps less appealing, large scale improved agricultural land management is likely to have a greater benefit than tree planting. There is plenty of evidence that much of our farmland is compacted and suffers from soil erosion caused by heavy rainfall. This approach has the additional benefits of reducing sedimentation and chemical run-off.
If tree planting and large woody debris in floodplains is going to be a solution then the benefits will need to be demonstrated, and the risk understood, to a far greater extent.
The official water quality data speaks for itself and is an indictment. Major improvements were made, almost 50 years ago now, in the lower catchment but the overall standards are now falling. A catchment cannot be healthy without good water quality and so I consider this to be the most important issue.
The causes appear clear, being mainly agriculture and, to a lesser extent, sewage discharges (both treated and untreated). There are few nature-based solutions unless you include having a lower reliance on chemicals on the farm and in the home.
Improvement can only come from improved agricultural practice, brought about by education and incentive, and backed by more effective regulation.
The catchment still has much to offer but it has been, and could again be, better.
Over recent years I have seen the decline of species such as curlew, sand-martin, eels, lamprey and trout. I have also seen an increase in invasive species such as the signal crayfish and Himalayan balsam. Otters appear to have returned and new arrivals like the white and cattle egret are generally welcome as long as they don’t replace the heron.
A major, probably the major, remaining obstruction to fish movement is the weir at King’s Mill Cullompton. Migrating fish species find this obstruction (almost) impassable.
Some parts of the catchment are noticeably low in interest, in particular the Spratford Stream, including the Halberton Stream. This is largely because of poor water quality.
In general, my support is for targeted action against undesirable species and for habitat improvement for desirable species. Put simply, “If we look after the rivers, the fish will look after themselves”. Fundamental to looking after our rivers is to have good water quality.
The Review provides an informative collection of the data and associated issues. Nature-based solutions can contribute to improvement, but only if they are complemented by more effective use of other measures and regulation, much of which already exist but is not being implemented. I look forward to seeing solutions, which will also need to be presented with clarity and rigour.