Property:Monitoring surveys and results
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R
As with the project as a whole the monitoring and evaluation is a collaboration between partners. Project objectives were used to set the method and frequency for data collection with monitoring results collated and evaluated by the ECP. Methods used include:
• Fixed point and drone photography, habitat mapping, vegetative surveys, riverfly monitoring and electro-fishing to monitor increases in habitat diversity and change in macro-invertebrate and fish assemblages.
• Electro-fishing, catch returns, red counts to monitor increase in Brown trout spawning on gravels.
• Fixed point photography and cross-sections plus flow measurements to monitor channel and morphological changes.
Photographs will be georeferenced and stored. Evaluated after every set of photos (in-house) and included in final evaluation report alongside all other data. An initial evaluation report will be produced at the end of 2016, with 3 year monitoring reports contributing to a final project evaluation on 2019.
Despite the relatively small scale of this project on the Glyme at Stratford (>1000mtrs restored) the upstream EA gauging weir has been used to demonstrate how the water level throughout the whole system has been raised by the restoration of the river. The increase shown is in the region of 0.2m. This means that the river spills out onto its floodplain earlier, slowing the flow of water and providing natural flood management downstream. This will also help by settling sediment out earlier during the hydrographic peak, benefitting downstream habitats and communities.
The catchment-scale effects of the scheme are apparent in the water level record some 5km downstream, at the River Evenlode gauging station at Cassington. Changes in storage in the river channel are transmitted downstream as water level variations at the gauging station. This signal is recorded at low flows.
Further post-restoration channel measurements and monitoring will be taken and evaluated to better quantify this initial interpretation of data.
D
Assessments of the ecological status based on nutrients, benthic algae, macroinvertebrates and fish were conducted twice, in 2017 and in 2020. The overall ecological status in 2017 and 2020 was bad due to lack of fish. This is due to a fish barrier (culvert) further down. However, macroinvertebrates increased from poor (2017) to good ecological status (2020), and benthic algae showed good status both years, thus these two organism groups had a good effect of the daylighting. Nutrients showed moderate status both years (Tot N and Tot P), which was the same as the upstream reference stretch.
Embankments were set in place to reduce the risk of bank erosion after daylighting, as this could lead to negative impacts on local buildings and infrastructure. 2 years of continuous monitoring of particle runoff in the daylighted stretch was compared to similar measurements at the upstream open section, and there were no differences in particle runoff from the two stretches.
To assess the recreational use of the area, the local bicycle club registered number of people using the new pathway and bench area every Saturday 10:00-14:00 from May-Oct 2017 and 2020. This showed an initial peak of users right after opening, then a slight decrease in 2017. However, the use was clearly higher in 2020, and the area was used by at least 9 people in the time registered every weekend in 2020. +
T
Assessments of the ecological status based on nutrients, benthic algae, macroinvertebrates and fish were conducted twice, in 2017 and in 2020. The overall ecological status in 2017 and 2020 was bad due to lack of fish. This is due to a fish barrier (culvert) further down. However, macroinvertebrates increased from poor (2017) to good ecological status (2020), and benthic algae showed good status both years, thus these two organism groups had a good effect of the daylighting. Nutrients showed moderate status both years (Tot N and Tot P), which was the same as the upstream reference stretch.
Embankments were set in place to reduce the risk of bank erosion after daylighting, as this could lead to negative impacts on local buildings and infrastructure. 2 years of continuous monitoring of particle runoff in the daylighted stretch was compared to similar measurements at the upstream open section, and there were no differences in particle runoff from the two stretches.
To assess the recreational use of the area, the local bicycle club registered number of people using the new pathway and bench area every Saturday 10:00-14:00 from May-Oct 2017 and 2020. This showed an initial peak of users right after opening, then a slight decrease in 2017. However, the use was clearly higher in 2020, and the area was used by at least 9 people in the time registered every weekend in 2020. +
Assessments of the ecological status based on nutrients, benthic algae, macroinvertebrates and fish were conducted twice, in 2017 and in 2020. The overall ecological status in 2017 and 2020 was bad due to lack of fish. This is due to a fish barrier (culvert) further down. However, macroinvertebrates increased from poor (2017) to good ecological status (2020), and benthic algae showed good status both years, thus these two organism groups had a good effect of the daylighting. Nutrients showed moderate status both years (Tot N and Tot P), which was the same as the upstream reference stretch.
Embankments were set in place to reduce the risk of bank erosion after daylighting, as this could lead to negative impacts on local buildings and infrastructure. 2 years of continuous monitoring of particle runoff in the daylighted stretch was compared to similar measurements at the upstream open section, and there were no differences in particle runoff from the two stretches.
To assess the recreational use of the area, the local bicycle club registered number of people using the new pathway and bench area every Saturday 10:00-14:00 from May-Oct 2017 and 2020. This showed an initial peak of users right after opening, then a slight decrease in 2017. However, the use was clearly higher in 2020, and the area was used by at least 9 people in the time registered every weekend in 2020. +
B
At one location, the introduction of trunks caused a more dynamic flow regime with deeper stream beds. At another location, the patches with dead wood filled up with sand, that had to be removed to prevent rising water levels. +
H
At the Houndsden Spinney it has thus far been impossible to collect road run off, so we have been unable to show an effect on water quality above and below the rain garden at this site.
Through our work alongside Thames Water and the EA to identify and rectify the misconnections blighting this site a significant improvement in water quality has been seen. We will soon be repeating invertebrate surveys to demonstrate this, along with public questionnaires which we hope will show an improvement in understanding of the urban water cycle and household misconnections. +
R
At the inception of the River Don Restoration project a need to improve confidence in the baseline data was identified. Whilst there was a significant amount of data associated with the Don we wanted to increase confidence levels in the data. In order to achieve this a baseline ecology study was carried out, as well as a baseline geomorphology report. SONDES (constant water monitoring equipment were installed) to gather baseline data in 2016. This gave a more in depth analysis of the condition of the river.
Since the baseline monitoring was carried out a number of river restoration interventions have been delivered. This has mainly included re-naturalisation of the river, improving fish passage and working with landowners to improve nutrient management in the catchment. Further river restoration will be delivered over the next 12 months, with significant levels of restoration to be delivered via opportunities presented though development.
Following on from this in 2020/21 further monitoring requirements have been identified through the Environment Agency’s Strategic Monitoring Review (SMR) which sets out localised monitoring requirements. In addition to the water quality monitoring an ecological and geomorphological assessment will be carried out to assess improvements and benefit realisation. +
C
Contournement d’un plan d’eau de loisirs sur le Gratteloup au niveau de la commune de La Ville-aux-Clercs +
Aucun état initial n’a été réalisé. Suite aux travaux,
un suivi annuel des frayères de salmonidés en aval et
en amont du plan d’eau a été réalisé.
Le lit et les berges du tronçon de cours d’eau en dérivation
sont stabilisés. Une ripisylve en rive gauche,
constituée de différentes essences d’arbres (aulnesfrênes-saules)
typiques de la région, se développe.
La granulométrie formée de graviers et de pierres
sur l’étendue de la zone est diversifiée. On y observe
l’installation d’herbiers aquatiques et de mousses sur
les pierres. Les systèmes racinaires des aulnes constituent
des caches et supports de pontes pour des
espèces piscicoles.
Le contournement du plan d’eau a permis de recréer
les conditions naturelles d’écoulement de la rivière
et de lutter contre le réchauffement de l’eau. Le
suivi des frayères en 2002 a permis la localisation de
plusieurs nids en amont de l’étang.
Depuis que le plan d’eau a été déconnecté du cours
d’eau, plus aucune vidange n’a été effectuée. La
vanne à crémaillère permet de maintenir l’essentiel
des particules fines provenant du réseau d’eaux pluviales
de la commune dans le plan d’eau.
Le plan d’eau est très fréquenté par les pêcheurs.
Cette opération unique dans le département est
toujours citée en exemple. +
D
Avant les travaux et dans le cadre du diagnostic, des
profils en travers et des mesures de débits ont été
réalisés sur le secteur à l’automne 2010.
Des pêches électriques ont été effectuées, en 2006,
2007 et 2008 sur une station dite « de référence »
(non influencée par un ouvrage et proche de l’état
naturel) au niveau de la commune de Saint-Souplet
(6 km en amont de l’ouvrage du Pont Fourneau).
Les suivis piscicoles (pêche électrique et indices ponctuels
d’abondance truitelles) ont été réalisés par la
Fédération départementale pour la pêche et la protection
du milieu aquatique du Nord (FDPPMA 59)
dans l’emprise de l’ancienne retenue (été 2011, 2013,
2015 et 2017). Le suivi piscicole se poursuit en 2019.
Lors de la réception du chantier et à nouveau en
2013, de nouveaux profils en travers ont été réalisés.
L’analyse des mesures topographiques a montré un
rétablissement progressif du profil en long de ce tronçon
de la Selle, une diversification des sections d’écoulements
et un retour à un gabarit du lit mineur proche
de l’état naturel dans l’emprise de l’ancienne retenue.
Les travaux ont ainsi permis au cours d’eau d’entamer
une dynamique de reconstitution d’habitats favorables à la vie aquatique qui a été rapide et efficace.
Dès 2011, le cours d’eau reprend un aspect plus naturel
au niveau du lit mineur et des berges. Rapidement,
des radiers réapparaissent, des macrophytes
immergés se développent, les berges se végétalisent
et une légère sinuosité s’amorce. Les plantations
réalisées reprennent rapidement et s’associent au
développement de la végétation rivulaire spontanée
pour couvrir les berges mises à nu suite à l’abaissement
de la ligne d’eau. Sept ans après les travaux,
les aménagements réalisés sont toujours en place et
les plantations en berges se sont bien développées.
Les premiers relevés piscicoles effectués six mois
après travaux sont encourageants : l’inventaire a
permis de recenser un peuplement piscicole intéressant,
notamment pour le chabot avec des densités
de 649 individus pour 100 m². Cette espèce préfère
les eaux fraîches et turbulentes désormais présentes
dans l’ancienne retenue plutôt que le milieu homogène
et envasé qui existait avant l’effacement de
l’ouvrage. Cette densité de chabot figure parmi les
plus élevées du département juste derrière la station
située en amont sur la commune de Saint-Souplet
(représentant un état de référence).
Concernant le suivi de la population de truites, entre
2011 et 2017, la densité de truite fario est passée de
3 ind./100 m² (2011) à 44 ind./100 m² (2017) et la qualité du recrutement en truitelles est passée de faible
(une truitelle en cinq minutes de pêche) en 2011 à
bon (16 truit. / 5 min de pêche) en 2017 en amont de
l’ancien seuil.
De la recharge granulométrique et un grattage des
frayères ont également été effectués en amont de
l’ancien pont, ce qui participe fortement à l’amélioration
de l’habitat et de l’aire de reproduction de la
truite fario. En plus de ces mesures, la fédération de
pêche a d’ailleurs obtenu le no-kill sur le secteur.
La commune du Cateau-Cambrésis et les riverains
sont satisfaits de la réalisation de cette opération notamment
du point de vue paysager et se sentent plus
rassurés par rapport au risque de débordement local.
En 2010, le SIAHSA a réalisé en parallèle une autre
opération de restauration de la continuité écologique
avec le démantèlement d’un second ouvrage
sans usage et en mauvais état, situé sur la Selle au
niveau de la commune de Solesmes (barrage Étilam,
ROE 75695).
Suite de ces actions, le plan de gestion de la Selle
2012-2022 a identifié 49 ouvrages perturbant la
continuité écologique, et notamment la migration
de l’anguille depuis l’Escaut. Le programme prévoit de traiter 37 de ces obstacles. En 2016, après les deux
premières tranches, 21 km de linéaires de continuités
sédimentaires ont été restaurés sur les 27 qui étaient
impactés en 2008. Grâce aux actions menées, ce sont
six ouvrages qui ont été aménagés et les vannes de
14 ouvrages ont été ouvertes. Les deux dernières
tranches sont actuellement à l’étude et ont pour objectifs
de se charger des 31 derniers ouvrages compartimentant
la Selle et ses affluents.
H
Awaiting upcoming report with survey results. +
B
Backwater effects and vegetation regrowth are being monitored. Results are not yet known. +
G
Backwater effects and vegetation regrowth are still being monitored. +
S
Baseline Geomorphology (Drone DTM & Bathymetry), Fish, Macro-invertebrate sampling, Small Mammals.
Repeat surveys to measure against the baselines.
*First records of spawning Brown Trout in urban Stoke-on-Trent.
*Increase in Harvest Mouse nests in the riparian zone.
*Increase in species diversity and abundance for macro-invertebrates. +
H
Baseline MoRPh10 survey undertaken in June 2022. Data available on Cartographer website
Post-project MoRPh10 survey to be undertaken in summer 2025 +
B
Baseline and wet weather phosphate, turbidity and dissolved oxygen monitoring and invertebrate monitoring.
Main findings:
-Phosphate concentrations measured during this study were high enough to cause WFD failure at every site, suggesting high levels of diffuse pollution throughout the catchment.
-Particularly high phosphate concentrations recorded during during dry-weather conditions in the lower reaches of the Ladden Brook, were accompanied by low dissolved oxygen and elevated turbidity. This requires further investigation as a high priority.
-Historic DO concentration in the Bradley Brook has steadily increased over the last 35 years, suggesting an improvement in water quality over time.
-The flood defence impoundment at Three Brooks Nature Reserve appears to be causing significant issues for turbidity and dissolved oxygen upstream in the Bradley Brook.
-There is a need for a future regular monitoring scheme on the brooks, including during wet weather events, if pollution sources are to be identified and resolved. +
S
Baseline data was collected as part of the Environment Agency’s Rural Sediment Tracing Project investigations. This data showed suspended solid loads in mg/l at five of the project sites. For each site, three readings were collected; upstream of inflow, at the inflow and downstream of inflow.
After completion of the project works, further samples have been collected and the suspended solid readings have been compared with the baseline data. Comparison of the baseline data with the post project work data demonstrates that the mitigation measures have been effective at reducing inputs of fine sediment at all of the sites. +
R
Baseline monitoring already carried out includes ground-based and aerial photographic surveys, timelapse photography of one LWS, drone topographic survey, macro-invertebrate survey, electro-fishing and salmonid redd counts. Water temperature loggers have been installed upstream and downstream of the project reach.
The surveys will be repeated at appropriate intervals. The redd survey done in November 2020 revealed new salmon redds associated with 12 of the structures - a very promising early result. +
G
Baseline monitoring has been undertaken by EA for fish and invertebrates. Sample site Stonebridge Close, Sedgewick Meadows and Queen Elizabeth Park. Impact will be assessed over time. +
R
Restoring the river continuity of the Bresle River by returning it to its original bed in Sénarpont +
Biological monitoring of this project is based on fish
populations. The pre-works situation was assessed in
2013 on the basis of an electrofishing campaign in
the leat. The assessment was carried out with redd
countst on the project site in 2013 and 2014, and in
2015 with a count in the upstream 8 kilometres of
river made accessible for fish by the works (the count
was carried out in a partnership with the Onema
salmonid centre). Post-works monitoring was done
from 2013 to 2015. Two inventories were carried out
in 2015 by the Seinormigr association, using the IAT
(trout abundance index) protocol. The initial and
post-works assessments did not implement identical
methods, i.e. the first was a fish rescue in the former
leat and the second implemented the IAT protocol.
The results are nonetheless useful on the basis of
individual density calculations.
The bypass of the Sénarpont hydraulic structure
made possible to restore the continuity of the Bresle
River a further eight kilometres upstream. The works
also improved the functioning of the alder and ash
wet woodland by enhancing the supply of water.
The operation also restored 650 metres of river by
reducing the impounded reach to 400 metres and
reinjecting water into a number of side channels
(250 metres). The connection between the riverbed
and the side channels in the project sector created
new expansion zones (in non-critical areas) for flooding.
These lateral connections improve water quality
through enhanced self-cleansing and the creation of
greater habitat diversity, a positive factor for biodiversity.
The former impounded reach was replaced by a
series of diversified flows in multiple channels in the
valley bottom. Fine sediment was removed to reveal
the coarse substrate that is now renewed naturally
thanks to the restoration of the morphodynamic
process.
Monitoring of fish revealed that prior to the works
in 2013, trout density was 0.5 fish per 100 m². In July
2015, after the works, the measured density was
5.6 trout per 100 m². The trout population gained
in numbers by a factor of 11 with a significant increase
in the percentage of the juvenile population
(30% of the total in 2013, 85% in 2015). The site has
thus become highly favourable for spawners and the
growth of juveniles.
At the end of 2013, just after the diversion of the
river to its original bed, several sea trout were observed
spawning in the restored channel. Five redds
for migratory salmonids were observed on the site.
One year later, a dozen redds were noted. During
the inventory, bullheads and eels were also caught.
The strong point of this project is the restoration of
the overall functioning of the river and of its side
channels for a relatively small amount of money. The
Bresle EPTB succeeded in defending its restoration
objective and in negotiating over a long period to
convince all the land owners and the town council.
Today, the results are positive. Local residents have
easier access to the nature and take pleasure in observing
a dynamic river with a diversified ecology.
This project was all the more beneficial that a number
of mill owners who were previously hesitant to
work on their installations are now ready to launch
operations to restore river continuity.
Biological surveys were conducted before works via a
fish inventory and invertebrates monitoring conducted
downstream and upstream of the currently restored
area. Monitoring measures after completed work were
implemented. These were taken in 2011 and 2012 and
covered the physical aspects - flow types, substrate, etc.
- on riparian vegetation, as well as the biological aspects
- benthic macro-fauna, fish population, insect fauna,
amphibians, birds and mammals. All these surveys are to
be compiled and included in a map database (GIS). The
monitoring will be conducted annually over a five-year
period (until 2016).
This operation decompartmentalises the Fontenelle
over 1.2 km and reopens access to the Rançon and the
Seine to biological communities between the confluence
and the next upstream weir on the Fontenelle.
Electrofishing analyses in 2011 show a recolonisation of
the area by brown trout. Functional spawning grounds
have also been observed in the rehabilitated site (observation
of brown trout reproduction in 2012). The
removal of the structure allowed recolonisation of eels
across the whole restored stretch. Upstream of the site,
eel density rose from 10.25 individuals / 100 m² in 2005
to 127 individuals / 100 m² in 2011.
Three months after the works, spontaneous aquatic
vegetation appeared; callitriche plants, marshwort and
common reeds have thus been observed.
Benthic invertebrates quickly recolonised the site.
Downstream in particular, groups characteristic of the
presence of organic matter - dominance of Gammaridae,
Diptera Chironomidae and Ephemeroptera - have
been observed, partly due to the significant and rapid
development of the herbaceous layer. Analyses in 2011
revealed the presence of Glossosomatidae caddisflies -
a group very sensitive to pollution - upstream of the
rehabilitated site.
The resumption of river dynamics with the appearance
of preferential areas of deposits and erosion is visually
apparent in the new bed. Compared to the initial situation,
flow types are more diverse, particularly on the
upstream part of the sector. The downstream sector
meanwhile flows through a distribution of rather lentic
water flows, owing to its slope, which are ten times
lower than upstream.
The risk of flooding is reduced by the presence of flood
storage areas covering several hectares along the new
course of the Fontenelle. The 10-year flood of 16 December
2011 provided the opportunity to observe this.
Two years after the works, a significant improvement
of the biological and morphological environment is observed,
with the rapid reestablishment of species and
the remobilisation of sediments. However, it is difficult
to have real perspective for the time being. The next
post-restoration monitoring will confirm or refute this
trend.
The success of this project depends in part on the major
coordination project set up by SMBVCS. Local residents
were involved very early in the project. The declaration
of public utility initially taken was not used, as all local
residents gave their approval.
With this renovation of the Fontenelle, half of its
course has regained its former bed. The river remains
perched over the whole 400 m stretch. However, the
restitution of the whole stretch into its original river
bed does not seem effective in terms of the cost-benefit
ratio achieved. The works would only concern a limited
potential surface of the spawning grounds and require
the end of fish-farming present on this site, which is of
local economic interest.