Property:Lessons learnt
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H
The road inlet designs had to be amended to capture water running along the gully with a road section cut out to allow a deep enough fall into swale. This has been rectified and the majority of run off is now entering the swales as designed.
The SuDS features are currently drier than anticipated. The resilient sedges are thriving, as are unwanted terrestrial plants. This has additional maintenance implications until replanting of edge species next spring.
Originally a much larger wetland was planned at this site to clean water in the stream. However the project had to be significantly scaled back as we were unable to provide data needed to the EA to approve the scheme, as collecting this level data would have been prohibitively expensive. It would be better in future to allow for longer lead time on the project and budget far more for pre-project monitoring, however in this case it is still unlikely that we would have been able to fund the data required. Monitoring of schemes such as the Salmons Brook Healthy River Challenge is imperative to provide proof that SuDS are a positive element in the toolkit of approaches to tackle urban diffuse pollution. +
E
The same integrated project team has worked on five separate flood alleviation schemes protecting four communities in Moray under the banner of Moray Flood Alleviation. These schemes represent an investment totaling £180 million over a fifteen year period. This has been key to the success of the project.</p>
<p>The project team operates a “continuous improvement” philosophy, using regular lessons learnt workshops to ensure that time and money is not wasted on avoidable mistakes in the future. Over the course of the project the team has developed a collaborative and efficient way of working. Currently the project is set to come in £10 million below budget. Four of the five schemes have been completed on time with Elgin scheduled to finish on time this year, 15 years after the start of the project. The project team has been co-located in the same open plan office throughout the scheme’s development and delivery ensuring matters are discussed easily and decisions are made quickly.</p>
<p>During the development of the design for the scheme, the implementation of the Water Framework Directive was in its infancy. Working closely with SEPA, the team were able to predict the implications of the Directive and design a scheme which complemented the requirements. Meeting with SEPA on a monthly basis has resulted in a sound relationship where issues have been discussed and resolved promptly.</p>
<p>The Elgin scheme has been shortlisted for the ACE/NCE 2015 Outstanding Achievement Award, which recognises schemes that have made a contribution to the reputation of consultancy and engineering. The team has also twice been commended by The Saltire Society at their Awards for Civil Engineering; in 2010 for the Forres FAS for a <i>“well managed and well executed FAS, constructed with high regard for the environment”</i>, and in 2012 for the Rothes FAS for <i>“the co-operation, goodwill and ingenuity demonstrated by the team, coupled with the response elicited from the community.”</i></p>
<p><i>“In more ways than one our community has been given a new lease of life and features have been created that complement the authentic architecture and public face of our village.”</i><br>
Rev Bob Anderson, Rothes Parish Minister</p>
<p><i>“I challenged the team to deliver flood alleviation and complement the environment. My measure of success was that the Scheme should be “invisible” and prevent flooding. Not only was the challenge met, but the Scheme was delivered ahead of programme and under budget. The team excelled and the outcome is very pleasing.”</i><br>
Peter Haslam, Moray Council
T
The sections of river that have been restored demonstrate the contrasting approaches of contractors working on different sites (see Image Gallery). The extent of channel narrowing and restoration works take into account varying views of the landowners, the aspirations of the fishery and the requirement to improve the SSSI. +
B
The sites were important for overwintering birds: teal, shelduck, tufted duck, wigeon, gadwell, shoveler, pintail, little grebe, common whitethroat, sandmartins, oyster catchers and linnet. Peregrine falcons also use the site.
Barking Creek is recognised as a valuable feeding and refuge area for a variety of fish species, flounder, eel, smelt, sea bass in both their adults and juveniles life stages. These utilise the full range of sub, intertidal and saltmarsh habitats for foraging and refuge.
creekmouth should not be located in the direction of the prevailing wind or litter can accumulate. +
N
The situation in the small urban Haukåsvassdraget is unclear. It will take time to achieve safe and stable good ecological conditions. Breeding and cultivation of freshwater pearl mussels is already a success. In order to succeed in returning mussels to the main river, water conditions must be improved. Supporting nursery habitats could supplement the conservation work. The mussel habitat at Haukås is an important trial project. +
L
The sluice at the Wet woodland presented some issues post project, with an unacceptable level of water loss through the frame. This was rectified and is now operating at a normal level. However, some thought must be given to the purpose of the sluice and this should inform the design of the sluice. Holding water back requires a strong but not particularly flexible structure.
Any back channel is relies heavily on the correct levels being established, this relies on understanding the local conditions i.e. any local impoundments this may not be easily recognized so early and often discussions with the EA or the local Drainage board are necessary. +
R
The success of the defined measures was hampered by three principal factors, firstly failure to engage local landowners early in the programme; the timing of key tasks, such as planting riparian trees; continued difficulty to control sources of environmental disturbance, in particular serious and continuous point pollution from animal husbandry. Consequently fish assemblages in all stream reaches were still dominated by aliens and highly tolerant species, and native cyprinids were low abundant or absent, revealing the fish index of biotic integrity a low environmental quality. +
L
The technique of installing Large Woody Debris at this site involved digging a trench securing up to a third of the limb in the trench with the remaining in the channel. By using the thicker end of the limb in the trench it left only the thinner branches in the river.
Ideally the wood shoul dbe as large as possible when in the river to ensure it will be long lasting and have as big an impact on the flows lcoally as possible. +
P
The timescales involved from conception to completion were longer than anticipated. The site presents a range of environmental sensitivities and land uses that required further consideration as part of the planning and physical works processes. +
B
The value of a multi-benefit scheme, through joint funding and agreed outcomes.
The value of good PR and information from an early stage in project development. +
N
The video summarising project work so far can be seen on YouTube: https://www.youtube.com/watch?v=1TcxL3JD6UQ&t=153s +
G
The wetland basin is quite large, sized for greater flows than have been experienced so far. This means that the water in the treatment basin overflows only during very heavy rainfall events. This is not a significant problem, it just means that the basin is acting more as an infiltration basin rather than a temporary storage basin. The system still functions to prevent polluted water entering the stream.
The plug planted sedges in the basin are thriving in this environment as the system was not fully activated until the plants were well established. However in the more shaded swales with greater velocity of flows and concentration of pollution the plugs have failed and need to be replanted.
Sedges have grown lush and verdant in the basin and water is cleaned and returned to the stream as expected or returned to the water table. Although perhaps not as aesthetically pleasing as in the design, the boulder arrangement at the head of the swales has worked well to slow water and prevent excessive erosion in the swales.
Water quality issues were far more significant than we had anticipated on commencement of the project, particularly in relation to domestic misconnections. High pollutant levels were evident beginning of our swales. We also found that although we proved our systems had a beneficial impact on water quality, just downstream of each project were outfalls which would bring in yet more pollutants. Therefore wetlands and SuDS alone could not demonstrate catchment level water improvements needed under WFD. Small scale interventions have a place in a suite of wider measures that need to be tackled with more drive, especially pollutant impacts from misconnections and vehicle use. +
L
The wide-ranging discussions held at the start of the project served to reconcile the different expectations and to allay the concerns of users. The solid technical feasibility study and the realistic impact assessment facilitated the acceptance of the project by all stakeholders and local residents. +
U
The work has resulted in rapid evolution of the site to a condition of improved physical heterogeneity (in-channel and wetland areas), with associated ecological responses. This has also resulted in a general aesthetic improvement, from a very simple canalised, embanked and perched channel to one that is much more physically variable, natural-looking and connected with standing water features (i.e. wetlands). The planting of trees in the riparian zone also benefits the site in this regard.
A practical benefit of the works was the improved protection of key areas of farming land from local flood risk. This was achieved through the removal of embankments on river right, permitting greater floodplain connectivity (with associated physical/ ecological benefits) to the east/ south of the channel while reducing pressure on the opposite bank. Furthermore, the implemented works greatly improved agricultural drainage; the bed of the restored channel was over 1 m lower than the previously perched condition, meaning that field drains could flow freely where they had previously been backed-up. Although not a primary objective of the project, considering these design objectives was essential to achieving buy-in by the local farmer.
There are also more general Natural Flood Management (NFM) benefits of the project. With greater floodplain/ wetland connectivity, there is greater inundation of areas adjacent to the channel under certain flood magnitudes. The storage of water in such areas will provide an increased level of protection to downstream areas. Furthermore, the re-establishment of native woodland will also contribute to NFM, adding roughness to the floodplain (slowing flows and increasing water storage times) and increasing the interception of water (surface flow and rainfall) through slowing flows and water absorption. Through such processes, the works will provide greater resilience to the effects of climate change. This is also the case for drought conditions; the previously homogenous condition of the channel has been replaced with a much more diverse morphology (particularly considering the wetland areas) that provides far greater potential for biotic refugia.
The work has generally improved the understanding of the benefits of such projects and the appropriate methods of their delivery. This has been a key case study for this type of work for SEPA and, with monitoring ongoing, dissemination of information will provide an invaluable resource to the wider river restoration community.
Given the explicit development of an integrated steering group and the associated project management approach, challenges during the project were minimised. Also, experience from previous construction projects by the design/ build team meant that many potential issues were avoided. There was careful planning of the construction phase of the project such that the most intrusive works (i.e. construction of the realigned channel and large wood implementation) were conducted ‘offline’, minimising the risk of high flow events impacting the works and fine sediment pollution. Such ‘assisted recovery’ designs explicitly require a degree of ‘field fitting’, allowing for unexpected issues encountered to be managed through appropriate short notice design variations. This was the case in the furthest downstream section of the site where, due to wet ground, it was not safe for construction machinery to excavate the initially proposed realigned channel in this area. It was therefore decided that the proposed design be modified such that the third (furthest downstream) wetland feature would be instated through this ~200 m long section, subsequently proving to be an appropriate revision. Such a short notice adjustment was only possible due to the close and established working relationship between the designer, regulator (i.e. SEPA) and contractor.
H
The work was carried out by a joint NRT/RGFA work party which enabled sharing of expertise between the two parties. +
K
There are no lessons learnt as yet.
We are keen to get insights from any similar projects targeting river flow restoration/support through perched reservoirs derived from upland mining operations. +
I
There are some significant limitations to Manning's equation, especially in waters that are heavily impounded as most Essex rivers are. This means that any attempts to use this equation to work out the flow and height of the water is limited, this adds a degree of complication to any water height and flow calculations. If this is the case, then water heights from specific days or contact with the local EA hydrologist is recommended to allow real time calculations to be taken at times of known flow. +
B
There is significant Archaeological interest on the site. With an identified Roman Villa remains in the local area. This adds a significant cost element to the project. Investigations are currently underway to identify the implications for this project but this may make the pond and wetland enhancement uneconomic. Early contact with the local Archaeological unit is recommended. +
H
These measurements show the potential of stimulating the origination of gravel beds. Actively introducing gravel would be a technological approach, which may be undesirable. If gravel is already naturally present in the stream, extra gravel may be added, but otherwise, a Building with Nature approach is considered more desirable.
Flow velocity variation can also be stimulated by main channel mowing or by introducing dead wood. When there is insufficient space for these natural measures, (as is the case for the Tongelreep), introducing gravel is an option. Providing sufficient shade over the gravel area is important. +
R
This has been a 3-year project. The partnership has taken that time to become established with clear objectives for the future. Partnerships of this size do take time. +