Property:Monitoring surveys and results
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R
Under objective 3 of the NIA walkover surveys to assess the habitat of the main Nene have been completed. Walkovers are also used to identify opportunities for habitat restoration. The river’s major tributaries are now being assessed.
So far three projects have been delivered:
*Duston, Northampton: marginal habitat has been improved upstream of St James End Weir.
*Rushton, near Kettering: a 45m-long backwater has been created by excavating part of an old meander loop.
*Orton Lock, Peterborough: an area of bank erosion downstream of the lock has been stabilised by “cutting & hinging” live willow into the scour holes and then adding further brushwood.
Restoration options on the main river are limited due to navigation and flood risk management. Proposed projects include the construction of fish easements on barriers, the excavation/re-connection of backwaters for fish spawning and refuges and improving urban marginal river habitats. +
Unfortunately no baseline was established before the measure was implemented and so far only a photographic monitoring was carried out, therefore environmental benefits cannot be quantified. However, a reduction of eutrophication was experienced, vegetation quickly recolonized the banks and the bed granulometry became more heterogeneous.
A quantitative monitoring is foreseen, especially of the river morphology and of the groundwater level. A quantitative assessment will support the implementation of similar actions in other sites using the same approach. +
S
Unfortunately this project was a capital project which did not allow for monitoring, however monitoring of the instillation of the bund and the large woody material to make sure if they have moved or are eroding. +
M
Up to date metals contents in soil, roots and leaves of the implanted herbs and trees are being monitored to evaluate the remediation capacity. +
R
Upstream reaches show well-developed riparian vegetation galleries dominated by alders Alnus glutinosa, willows Salix spp. and ashes Fraxinus angustifolia, but below the dam, in the considered segment, banks are collapsing because of the fluvial erosion and agriculture (with dominance of orange orchards) and the invasive giant-reed Arundo donax finds here the appropriate conditions to spread even if Mediterranean sclerophyllous and evergreen scrub as well as cork oaks are still the characteristic landscape. Fish assemblages include a pool of native species, where we face the reduction of two endangered cyprinids _Iberochondrostoma almacai and chub Squalius aradensis. Other native species are present like the loach (Cobitis paludica), eel Anguilla anguilla and Barbus sclateri occurs sparsely (Pires et al., 2010). The degradation of habitat and water quality have given an increasing role to the highly abundant mosquito fish Gambusia holbrooki, and pumpkinseed Lepomis gibbosus, largemouth bass Micropterus salmoides, chameleon cichlid Australoheros facetus, carp Cyprinus carpio, and straight-mouth nase Pseudochondrostoma polylepis. The American crayfish has extended also its dispersion area after the artificial reservoir.
A laborious appraisal of the problem was assessed in all catchment by using different layers of information related to geology, climate and soil cover which allowed to define the physiographic units. Other layers containing descriptors of disturbance (habitat modification, roads, point and non-point pollution) allowed to define those units where rehabilitation should take place. The designed measures to stop the enlargement of the river channel, in the most critical reaches were based on soil engineering techniques after the convenient bank reprofiling, such as vegetated gabions and rip-rap and cribwall to stabilize the banks, whereas the invasive cane was controlled by a double-matt (organic and synthetic) of bio-degradable geotextile after clear cutting. In these places were also conducted an extensive plantation of riparian trees and shrubs to improve those measures and to control the advance of the invasive giant-reed. With that purpose plant material was collected in the area of the reservoir (before it was filled), and a plant nursery was created. Therefore there was a strict genetic control and plantation of trees (mainly ash trees and willows) and shrubs (such as Tamaryx and Oleander spp.) followed the observed longitudinal succession in previous surveys.
This study applied 2-D hydraulic simulations to evaluate the habitat improvement of two the two mentioned endangered cyprinid species, resulting from the implementation of distinct instream structures – i) placement of three islands in the middle of the river channel; ii) introduction of two lateral bays on opposite banks; and iii) introduction of four alternate current deflectors - in a modified river reach of a Mediterranean river. Though the use of such instream structures has been considered in many habitat improvement projects (e.g. Vehanen et al. 2003; Garcia de Jalón and Gortázar 2007), no previous analysis of their potential effectiveness on fish habitat has been carried out in non-salmonid rivers. This information can prove extremely useful elsewhere, namely in other Mediterranean-type rivers, where the implementation of instream structures and compensatory measures as a means of recovering other threatened fish populations has been questioned. The River2D model (Steffler 2000), was used with this purpose: This finite element model simulates hydraulic conditions from topographic data input and uses the habitat suitability index curves containing known fish biological preference data, to calculate the potential habitat for specific life-history stages by the Weighted Usable Area (WUA).
The habitat improvement measures were concluded in the end of spring 2012, and monitoring to assess its efficiency was conducted in specific periods in 2013 and 2014, which were compared to the previous situation. Such monitoring considered the succession of floristic communities in the river corridor, as well as in the aquatic habitat, where the surveys included benthic communities and fishes. In both years all sites were electrofished (DC, 300–700 V) during late spring−early summer base flow. In this period stream flows were lower (but still had full connectivity between habitats), thus ensuring a higher fishing efficiency (Oliveira et al., 2012). Electrofishing distances followed CEN standards for assessing fish species composition and abundance for wadeable sites (CEN, 2003). This distance was at least 20 times the mean wetted width of the channel to encompass complete sets of the characteristic stream form (e.g., riffles, pools, runs) with a minimum sampled length of 100 m. The entire widths of streams were fished by wading slowly upstream during daylight, using natural barriers, mostly shallow habitats, to delimit survey zones. To compare changes in fish communities and to evaluate the biological quality of sampled sites we used the fish-based index of biotic integrity for Portuguese wadeable streams (F-IBIP) (INAG and AFN, 2012).
In the two-year study it was collected 11 species of fish (seven native, three exotic and one translocated taxa), representing a total of 4521 individuals. In both years fish communities were clearly dominated by three species (A. anguilla, C. paludica, and G. holbrooki), which represented more than 70% in almost all samples. The populations of native cyprinids have always represented a small fraction of the communities, although they were present in all 2011 sites; however, these species were absent from segments E and K in 2012, the most degraded stream reaches of our study. The abundance of alien species varied considerably between segments and years, but generally represented a relevant proportion (> 25%) of the total species. Our results also seem to indicate a dispersion of the translocated species P. polylepis – an endemic species to central Portugal – with the number of occurrences increasing from 2011 (one site) to 2012 (three sites). Thus, independently of the year of study, all segments presented highly degraded fish communities, dominated by very tolerant species, with low proportion of native invertivores cyprinids and native lithophilics, and with a significant presence of alien forms. Results of the F-IBIP calculation reflected these observations, with all stream reaches presenting bad or poor biological quality in both years; in three of the segments (E, K, M) the F-IBIP score was even lower than in 2012, decreasing from poor to bad.
O
Vegetation development is monitored by FLORON. In the Overijssel kanaal, reed removal has created opportunities for the development of calamus and yellow iris. Macroinvertebrates are monitored at 3-4 locations per stream as part of a regional project in the Marswetering, Overijssels Kanaal and Beentjesgraven. The overall ecological quality ratios of the three streams have improved. +
B
Vegetation development is monitored by FLORON. Vegetation development is monitored by FLORON. Macroinvertebrates are monitored at 3-4 locations per stream as part of a regional project in the Marswetering, Overijssels Kanaal and Beentjesgraven. The overall ecological quality ratios of the three streams have improved. +
S
Very accurate baseline surveys have been completed. Preliminary assessment indicates a current rate of retreat of the banks at around 1m per decade, or approximately 10cm annually. A large amount of material has accumulated behind the spiling and facines which are being well maintained. Additional work, installation of supporting posts and fascines, has commenced on the east side of the island. +
D
Visual inspections and photographs of changes. It is clear that even with a resistant clay bed some of the narrowing structures have created scour pool formation. +
T
WFD baseline data
River profile surveys
Drone images from above before and after - aerial
Fixed point photos before and after land
Fish survey in new channel and invertebrate surveys to be carried out 2018 to see what is in the channel +
B
Water and biodiversity monitoring each 10 days, specially waterbirds. Restoration and management have boosted local endangered waterfowl populations and eased the colonization of new species for the Albufera wetland. Breeding populations of othe species than birds have established (reptiles and insects). +
3
Water chemistry testing was regularly undertaken as part of the project to help identify phosphate sources. This testing was undertaken by Westcountry Rivers Trust and Students from Plymouth University. A more detailed study of metals in these rivers was also undertaken to help to understand more fully the historical issue with regard to heavy metals in the catchments. +
H
Water depth, flow velocity and substrate cover were measured four times in 2016/2017. In addition, the position of the gravel beds was measured twice per year in the years 2015, 2016 and 2017. These measurements also revealed limited sedimentation, which was 80% gravel in late 2017. The gravel areas moved by on average 1.0m (+/- 0.3m), indicating that they mostly remained in place over a five year period. After the introduction of gravel beds, total species abundance and the number of species typical for an R5-type stream both increased significantly.
Source: http://edepot.wur.nl/468347 +
B
Water flow and temperature is logged every hour
Benthos and fish will be monitored yearly by NIVA.
The first salmon fry was observed two days after the channel was opened.
One month after there were fish in the whole side channel: A. salmon, brown trout and flounder. There were three cohorts of A. salmon observed: 1+, 2+ & 3+. +
A
Water immediately started to spill out of bank picking up a network of relict channels within the floodplain. Subsequent high flow events have seen gravel depositing instream and as shoals, more dynamic flow patterns and a complex of side channels, permanent and temporary pond features.
Prework aerial studies of the area and fixed point photography at key areas through the valley have allowed a gross study of early geomorphological changes within the system, including stream number and width, and changes within the network of wet areas across the valley floor.
Aberystwyth University are undertaking flow measurements and will continue to do so over an extended time period. Ecological studies will be undertaken across this and a control site on the same water body to monitor changes. +
J
Water levels downstream of the wood packages are higher and fluctuate more downstream of the wood package. This may be caused by the increased flow resistance due to the dead wood, leading to a higher water level for the same discharge. Water level peaks downstream of the wood package are smaller relative to the average water levels. This may because of water retention by the wood packages. As a result of the introduction of dead wood, sandy substrates have become less dominant and silty substrates have become more prominent. No change in nutrient levels was observed. A change in species composition was observed, but this change was short-lived. A subtle change in macroinvertebrate composition remained for a longer period afterwards. +
T
Water levels, stream discharge, bed profile and ecological parameters are regularly monitored. +
D
Water quality indicators are monitored for compliance with Water Framework Directive goals. In addition, the hydrological and ecological effects are monitored as part of the 'Building with Nature in streams' project.
So far, suspended maintenance has led to the establishment of an alder carr (Dutch: Elzenbroekbos). It is likely that the dry summers of 2018 and 2019 have caused some ecological damage due to the stream running dry. +
P
Water quality monitoring is showing improvements in dissolved oxygen since the restoration work - see DO chart below.
Invertebrate monitoring undertaken in Spring 2012 before works commenced gave a very low BWMP score of 7/200. Biological sampling will be repeated in Spring/Summer 2014.
Changes in public opinion of the brook prior to and after the restoration scheme have also been recorded - see survey results below. +
B
We have been monitoring the effectiveness of silt traps within the system along with taking water sample for chemical analysis. In addition we have undertaken BMWP sampling for freshwater invertebrates as well as ecological surveys for reptiles and amphibians, fish, birds, dragonflies, bats, harvest mice and macrophytes. All of these were also undertaken for 2 years before the project started to generate a baseline status for the site. Results show that, across all parameters, water quality is significantly improved and that the sediment traps are working in all but the most extreme flow conditions. Species diversity across the site has grown from a recorded 100 species in 2017/18 to 535 species in 2021. Five fish species have been recorded within the new channel (from none within the old channel). The site has also recorded the first Scarce Blue Tailed Damselfly in Sussex for 125 years, one of 18 species of Odonata now recorded on the Brooks. Water quality sampling has revealed significant amounts of nitrate being released from the aquifer over winter which has highlighted a need for further investigation of land management practices to the north of the project area.
We have also been monitoring impacts on the local community and results show a better appreciation and understanding of the water environment, that co-design and delivery has ensured guardianship of the site into the future and that providing outdoor opportunities in heavily urbanised areas is of great value to wellbeing and community cohesion. All results of the project will be available on the website from January 2022 - www.oart.org.uk/epic +