I can’t see the useful document you refer to but would be interested to see it as we are currently improving our paperwork to ensure our projects are CDM compliant.
I recently attended a CDM training course and just wanted to clarify that CDM applies to all construction projects regardless of size. A project being ‘notifiable’ to HSE does only apply to larger projects (30 days/500 person days) but all construction projects fall under CDM and there are legal duties under this for the ‘client’, the ‘designer’ and the ‘contractor’, of which the Rivers Trust could be any one or all of these.
Leaky dams may not class as construction if they are simply forestry operations of felling a tree across the watercourse but if a ‘structure’ is created the work will fall under CDM.
In answer to your original question I haven’t heard of any issues around CDM with small projects and a simple record of information exchange and risk assessment for the work is likely to be sufficient.
I had a similar situation where there was an opportunity to install leaky dams but the landowner couldn’t have the water spilling onto the surrounding farmland. The watercourse/ditch was quite deep so we just made dams (a series of 5) which are below the top of the bank, but they work really well. There’s a few photos here http://www.westcumbriariverstrust.org/projects/dovenby-project but I’ve got lots more photos of them in storms showing the difference in water level upstream and downstream of the dam without any damage to the farmland. Let me know if more photos would be helpful and I can send some to you. caitlin”at”westcumbriariverstrust.org