The write up of the introduction to the project can be viewed here.
I have now returned from being out at Richmond Park delivering the first phase of restoration to the Beverley Brook in Richmond Park. It has been a while and lots has happened which I am keen to share. I suggest you make a cuppa, take a seat and get comfy.
The Beverley Brook possesses incredibly flashy characteristics due to the urban nature of the river with a significant proportion of the catchment being coated in hard, impermeable paving. With the plan to be on-site for seven weeks through the British autumn undertaking a significant amount of in-channel works to 600 m of river, we were firmly in the hands of the weather once again.
The aim of the project is to enhance the heavily degraded, uniform and generally inhospitable channel so that it would be more inviting to the native fauna and flora that should be present and abundant.
A sorry state at the start of the project
Before the works started we undertook a range of monitoring to capture the baseline condition of the river. These will be vital and incredibly interesting to refer to in the years to come to demonstrate the effectiveness of the project. The monitoring included a two day fish survey undertaken by the Environment Agency, habitat mapping, aquatic invertebrate and plant surveys, sediment analysis and novelly for us, a drone recorded aerial video and photography of the site with some exciting low fly-over manoeuvres.
The work then commenced. With the help from the Aquamaintain guys once again and with Trevor behind the controls of the long reach excavator, we set about spicing up the bland channel. The key to this was variety. A variety of flow types, a variety of channel widths, depths and bank profiles. By adding diversity, a mosaic of habits would be created, providing for a range of species throughout their life stages.
When discussions about the project first started with the Royal Parks a year or so ago, I could not believe my ears when they announced that there was no shortage of trees and rootwads we could source from the Park to use in the river. With this rare offer, I was like a kid in a sweet shop. With the help of Mick Baker, the Park’s go to forester, dozens and dozens of oak trees were felled (I must add this is as part of the Park’s management regime), the root balls dug up and all carried down to the river by the mighty forwarder (tractor).
Rootwads and LWM ready to be used
Some of the LWM stockpile seen from the air
Mick bringing down another load of oak tree tops
The wood was introduced to the river in a variety of methods to perform a number of tasks. In places, masses of the tree tops and smaller limbs were stacked up against the bank extending between a third to half way across the channel. These were compacted with the huge force of the excavator and then secured with posts and fencing wire. This technique reduces the channel width to give the river more energy whilst providing complex habitat both above and below the water line. Furthermore, the dense network of branches creates slack water, encouraging silt to drop out whilst also capturing leaves and seeds. Overtime, these structures will consolidate and vegetate to form a new bank. By alternating the bank these are constructed on, a meandering sequence is created in conjunction with the next method, backfilled faggots.
Tree tops and brash in the foreground before being compressed and secured
Faggots (brash bundles) are fixed to the bed with posts and wire to create the new bank line, again reducing the channel width in places from 7 metres down to 2.5. The steep banks are then regraded and the spoil placed behind the faggots to produce low lying berms which in time will become wetlands when marginal plants establish.
Faggots with incorporated LWM being used to narrow the over-wide channel before being backfilled with the regraded banks
Protruding out of the tree tops and faggot berms, larger tree trunks, rootwads and multi-limbs (Large Woody Material, LWM) where fixed into place, extending out across the channel.
Rootwads providing complex cover with a backfilled faggot berm behind
Doing so is a great way to not only provide complex cover but is also a way to reinstate energy back to the river. As water rushes over, under and past the structures, the bed is scoured, creating deeper holes and throwing up the cleaned gravels into shoals and bars. This is a truly rewarding aspect of the work, identifying where and how to place the wood. Even under low flows, the impact can be felt immediately with the gravels being kicked up around your feet. A day later, the bed downstream is glowing with gravels as opposed to the previous uniform blanket covering of sand. And again, after higher flows, features are carved out and created.
LWM immediatley forming holes, shoals and riffles
The banks were also naturalised as we progressed downstream. The steep gradient was reduced where possible to provide transitional areas between the terrestrial and aquatic habitats. Intermittently, hugely over-engineered concrete headwalls with tiny two inch blocked land drains poking out scared the bank. Being redundant, these were removed with a total of 20 tonnes of concrete being mucked-away from site.
Another concrete headwall being removed
Significant regrading of the perched banks to form a wide wetland area on an inside meander, soon to be planted
A key aspect of the project is to restrict deer access to the channel. To do this the entire 600m length which is divided into two sections was fenced off. However, to prevent them accessing the stretches by simply walking up the channel, we had to construct river gates at the ends of the sections. In a river as deeply incised and flashy as the Beverley Brook is here, this took some doing. We ordered in several chunky telegraph poles. Some were cut and notched to form half jointed A-frames. These were positioned in deep holes high up on the banks. Mounted onto these, the excavator lifted 12 metre telegraph poles to span the channel. From these using stainless steel eye bolts and chains, oak gates from wood sourced and milled in the Park and manufactured by our good friend, Norm Fairey were hung. The principle being that the river gates prevent deer passing but importantly not causing a debris build up.
A section of the 600m of fencing which has been erected
The moment of truth, the telegraph pole spans the 12m gap before the braces are removed from the A-frames and the holes are filled with concrete
Jack standing back and admiring one of the three telegraph pole river gates completed
A conveniently placed bridge provides the structure for the fourth set of gates
The last task was to create a deer and dog access point. These access points prevent the banks being eroded (poached) with the subsequent input of sediment to the channel. The banks were regraded to a shallower angle and first armoured with 20 tonnes of gabion stone and then covered with compacted scalpings.
Access point in the foreground with the most downstream river gates behind marking the end of the restored section or river
As I mentioned at the beginning, we were needing the autumn weather to be kind to us. Who could believe it? Throughout the first three and a half weeks we barely had a drop, allowing great progress with the in-channel works and with ground conditions holding up well. After that, we did lose a couple of days due to rain and the spatey flows but I considered we had been lucky and gratefully accepted it.
The New Year has provided the first heavy flows. I managed to get down to the river yesterday and waded the length inspecting how things are bedding in. I am pleased to say that the restoration has certainly been successful in the aim of providing variety. With more energy, the river at last has active functioning processes.
And after, variety is the spice of life!
The Large Woody Material is scouring holes with loose gravel riffles forming downstream. The bed on outside of the meanders is deepening with large deposits of sediment forming shallow berms on the inside. The tree tops are accumulating sediment and consolidating quickly. The water’s surface is rippled and broken making the river audible once again. Even whilst doing the work, each morning a walk up the river demonstrated the immediate effectiveness with dace and chub taking up residence in new lies and pools where before there were none. I am thoroughly looking forward to seeing how the river adjusts and naturalises over the coming weeks, months and years.
So moving on, next month we start addressing diffuse urban pollution entering into the Brook from the A3 by digging a sediment trap and creating two wetlands. We are also having our first of several planting days. This one introducing trees to the river banks to provide shade and Large Woody Material in the future. We will keep you posted.
There are so many people to thank. The funders; The Friends of Richmond Park, The Royal Parks, the Environment Agency and the Beverley Brook Catchment Partnership. And those that helped out; Simon, Julia and Adam at The Royal Parks, the guys at Aquamaintain; Ben, Dave, Jack, Zac, Lloyd and Roo. Trevor from Land & Water in the machine, Norm Fairey, Curling Fencing Contractors, Mick Baker, Andy Birnie, Colin Hampton, Luke and his drone, the list goes on. Thank you all.