Property:Lessons learnt
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P
This has demonstrated that river restoration can be achieved by private developers as a cost-effective mitigation measure. The construction cost of the scheme, mostly earthworks, was approximately 5% of the total.
It is important to show that these types of schemes can be delivered effectively by private developers, in close consultation with other stakeholders. This complements other river restoration work being undertaken by the public sector.
Finally, in the process of facilitating development (which assists in economic regeneration) these types of restoration schemes can contribute a range of ecosystem services including supporting services (habitat creation; biodiversity); regulating services (flood control) and cultural services (potential recreation and amenity through riverside walkway; tranquillity; and educational services through being used as a demonstration project). +
R
This is a constant battle, it is something that needs to be undertaken each year. There was no action in 2008 and this saw a huge increase in the presence of pennywort. As the occurrence of the plant becomes less the time and cost associated with the project also decreases. +
P
This is a small project, total cost is expected to be less than 5k. However, it still has to be treated as if it is a major project. This has led to a very bottom heavy project with a substantially more spent on the consenting process rather than the delivering the project. There is a strong argument to suggest that any river restoration project must be worth the consenting process and smaller projects may not offer value for money. +
S
This is the start of a 6-year programme of flood risk management works within Leicester. The Soar is navigable in Leicester and as most work was undertaken to improve conveyance we were limited in what improvements to marginal habitat could be undertaken. Most work involved wetland creation within the river corridor and creation of backwaters. Going forward future flood schemes on the Soar tributaries should look at the in-channel and marginal habitat improvements which should help to have a greater impact on WFD classifications.
Leicester is home to surprising amount of protected species for an urban environment. A lot of monitoring work was undertaken and careful consideration given to this during construction. This is something that will feed into future work to ensure that new foraging habitat created is not affected by subsequent work.
Leicester has a very diverse community which speak a large number of languages and for many English isn't their first language. A lot of the information we are trying to convey is in English which means that especially in tackling issues around diffuse pollution the message may be lost. We are looking at ways we can be more effective in getting the message out by doing work with schools and community groups who can then pass the message on. +
L
This makes LORP a shining example of how natural processes can be harnessed to provide multiple benefits to wildlife, the environment, and people. By working with nature, the project is helping to create a more resilient, sustainable, and brighter future for the Otter Valley, its estuary, and surrounding communities.
Through these natural solutions, LORP demonstrates that it is possible to adapt to the challenges of climate change, reverse significant habitat and biodiversity loss, and improve degraded systems by working alongside nature, rather than against it.
The project is not only improving the ecological health of the Otter Valley and Estuary, but also providing important socio-economic benefits for local communities, such as improved flood resilience and infrastructure, and enhanced wellbeing, health, and recreational activities. +
F
This permeabilization
represent an
improvement in the
longitudinal
connectivity of this
river reach, however
it is considered
necessary to
permeabilize the weir
located 3 km
downstream in order
to achieve a more
complete
reconnection. +
U
This project did pose some issues during its delivery. The extent of the berm creation and bed reprofiling was limited due to the presence of overhead power lines. A safe working method was implemented by the Ops Delivery team. Initially the excavator to be used had an 8m reach; this was also used on the North Channel job. However this reach was wider and to maximise the benefits of the project a long reach had to be brought to site. This came at additional cost but enabled effective delivery of the project. The long reach machine was also used on a few parts of the North Channel project which were out of reach form the original machine. The tree works described above were also able to be carried out with the larger machine. +
This project did pose some issues during its delivery. The generally narrow nature made any changes made to the bed more sensitive than in other reaches of the Frome. The existence of gravels within the river bed was not as extensive as first thought. There were sections that were mostly clays which made it harder to reprofile effectively. The decision made on site was to minimise or exclude any works to the bed if gravel quantities were low.
The banks of the channel were high and steep; they were also quite soft so when trenches were dug to install LWD structures the banks in places seemed quite fragile. This limited the angle which could be dug and did restrict the use of this technique in places on the reach.
The benefit of adding value as described above cannot be under estimated. As described it can give a project additional materials (tree limbs etc) but can also gain acceptance of the project by other stakeholders such as the tenant farmer or river keeper. These can be achieved with minimal additional cost to the project. +
R
This project had a range of key challenges that were overcome through the design process, including:
• The restoration of natural hydromorphological processes whilst minimising the potential for large scale channel migration. This was resolved through the design of a multi-stage channel which allows the low flow channel to adjust within a more permanent high flow bank line. Seeded gravels were also allowed to rework naturally to create a wide range of in-channel habitat niches. The two stage channel safely accommodates both the low dry weather flows and the high flood flows.
• Ensuring that the river could be re-meandered through contaminated land at the site without increasing remobilisation of in situ contaminated sediments and leachate. An uncontaminated capping layer using uncontaminated soils was used to protect the environment and park users from contaminated materials.
• Minimising the need for expensive off-site disposal of contaminated materials and the need to import uncontaminated soils for capping. Soils on the site were categorized as contaminated and less contaminated (i.e. with contaminant concentrations below hazardous levels), and the former were used as a base layer for landscape features within the park. These were capped with less contaminated soils from the site to prevent exposure to the wider environment. +
W
This project has benefited from detailed investigative work and consultations that were undertaken as part of the site selection, scheme design and impact assessment work as well as for the preparation of the monitoring programmes. However, the need to find such a large site that met all the requirements was a long-term and costly exercise. There has been a full time project manager with supporting teams including representatives from statutory and non-statutory authorities and these aspects have enabled problems to be foreseen and rapidly addressed. The team approach has also allowed innovative new design elements to be identified which should provide high value at low cost (e.g. the island features in the site and a new ‘heterogenic’ borrow-dyke design).
The initial monitoring is still ongoing, and the full results from the first five-year monitoring programme have not been reported yet. However, from the interim progress reports that have been produced by ABPmer and Jacobs up to the end of 2010 (i.e. up to four years after the breaching), the following general observations have been made:
Breaches and channels: The breaches and channels through them are very stable which confirms the effectiveness of the approaches that were taken to design them.
Accretion: Within the site, sediment accretion has occurred relatively consistently and evenly due to the slow flows and stable internal creek/channel configurations. In the first year after breaching (2006 to 2007), accretion was around 10cm (of which about 50% is considered internally relocated materials and 50% externally imported sediments). In each subsequent year, the annual accretion is considered to be predominantly related to imported sediments and amounted to 3 to 5cm on average (specifically 5cm in both 2008 and 2009, and 3cm in 2010).
Invertebrates: The accretion and the relatively stable and depositional nature of the environment has helped to promote rapid benthic invertebrate colonisation of the mudflat (approx 80ha in extent). After the first, year invertebrates abundance was at 20,000 organisms/m2 and has ranged between 10,000 and 20,000 organisms/m2 in each successive year. The benthic assemblages have been dominated by large numbers of mud snail (Hydrobia ulvae) and although the patterns of organism recruitment are clearly complex and variable, there is evidence that the assemblages are maturing over time. This is indicated by the bivalve species becoming an increasingly important component over time (representing 2%, 4%, 14% and 26% of the populations in each successive year).
Birds: The bird monitoring (by CJT Ecology) shows that over the course of the four completed years of the monitoring programme the site has been supporting very good numbers of waterbirds. This was the case even from the first winter survey (2006/07) when the site supported around 7,000 waterbirds and included good numbers (i.e relatively high in a national or international context) of many key species such as shelduck, dunlin, black-tailed godwit, ringed plover and golden plover. In the following two winters the value of the site continued to improve as the abundance of waterbirds increased to around 10,000 and then 12,000. For the most recent winter (2009/10) however the overall abundance levels declined slightly. These broad trends are strongly influenced by some major inter-annual changes in the abundance of certain species which, in turn, are likely to be influenced by the weather conditions (e.g. particularly bad weather conditions were experienced in 2009/10 when compared with other years) and/or a range of other factors that influence the natural dynamics of bird populations (e.g. breeding success, timing of migrations, national population trends and inter-annual or inter-generational changes in roosting/feeding site selection). It is of note however, that the numbers of birds using the site as a roost reduced in 2009/10 while the number of birds feeding increased. This may indicate that the habitat and the relationship with migratory birds is still maturing and developing or that under adverse weather
conditions the site’s value as a feeding site as opposed to a roosting site increases.
Saltmarsh: Saltmarsh coverage of elevated areas of the sites (approx 25ha in extent) has occurred relatively rapidly. On average plant coverage (i.e the amount of marsh plant compared to bare mud at any given location) has rapidly increased from less than 1% in 2007 to 6% in 2008, 60% in 2009 and finally at or around 100% in 2010.
E
Thus, the experimental flood release showed limited geomorphic
benefit, despite reaching (or even overtopping) the channel banks. Most
changes were related to the transport of fine sediments, but they did not
enhance habitat variation, or create new fluvial forms. Cebrián et al.
(2015) suggested that the results may have been associated with
extensive modification of the channel after six decades of dam management.
Bed incision or unbalanced river morphology could be hampering
the geomorphic influence of ordinary flows, requiring higher flows than
theorised to enhance sound morphological and ecological changes. +
Timing of the project - advice would have been more beneficial if delivered during 2015 earlier in the season. Also, the length of the project limits the scope of work which can be carried out. +
S
To add +
R
To be used as a reference in river restoration science on how to re-establish a natural flow regime in other European river systems near urban areas. +
U
To get maximum benefit from projects, in areas with less constraints, we needed to look wider than interventions focused just within the channel and consider the floodplain as well. Further learning for individual projects can be found in the project specific case studies. +
R
Too soon to say - this section will be updated when monitoring reults have been evaluated. +
Undertake a Level 2 archaeological survey prior to demolition
Ensure landowners and fishery owners are on board in the early stages
Evaluate likely channel impacts from proposed modifications prior to demolition so no significant supprises +
L
Upon completion of the project, the following results have been listed:
+ More than 10,000 fish are using the fish passages. 80% of fishes which try to use the vertical-slot fishway achieves it, 50% does it in less than half an hour.
+ First weir removal within the Segura Basin
+ Volunteer collaboration and the landstewardship scheme are essential for the achievement of a favorable development of the riparian vegetation. In case of volunteers, thanks to its implication in plantation and refered to landowners for their commitment to properly mantain riversides and to avoid the development of alien species spots as in the case of Arundo Donax.
+ Results obtained by the removal of Arundo Donax have been diverse, depending on the area and the technique applied.
+ Plantation has been more effective for willows (Salix sp), poplars (Populus sp.), elms (Ulmus minor), mastic trees (Pistacia lentiscus) and rosebay (Nerium oleander).
+ A proper implementation of the plantations, a good size of the holes, the location of each plant and the time of plantig are essential for the succes of the works.
+ One of the most succesful achievements has been giving visibility to the problem and to the project and the social awareness about it. +
C
Use larger woody material for leaky dams.
Ensure stone blockages are installed above flood level to prevent scour and the the clay covering the bund from being washed away. +
R
Utilise the material within the channel where possible to reduce the costs and impacts of importing foreign material. +