Bristol and Avon Rivers Trust
Somerset Frome Catchment Walkover Report
June 2014
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Document: Catchment Walkover Report
Project: Somerset Frome
Client: Bristol and Avon Rivers Trust
Project number: 1667
Date of issue: June 2014
Prepared by: Ahern Ecology Ltd Unit 13 Hurricane Close Old Sarum, Salisbury SP4 6LG Website: www.ahernecology.co.uk Email: [email protected] Telephone: 01722 580008 Project manager: Rachel Whatmore
Field team: Rachel Whatmore, Adam Ellis, Jessy Grant, Simon Browning
GIS: Rachel Whatmore, Sean McGrogan
Document checking
Primary author: Rachel Whatmore Signed:
Review by: Daniel Ahern Signed:
Approved by: Daniel Ahern Signed:
Catchment Walkover Report Ahern Ecology Ltd
Contents Commented [AE1]: Update ‘page numbers only’ when finished Executive Summary ...... 3 Double check formatting as font etc sometimes changes on updating 1.0 Introduction ...... Error! Bookmark not defined.
1.1 Introduction ...... 4
1.2 Background ...... 4
1.2.1 Water Framework Directive (2000/60/EC) ...... 4
1.3 Somerset Frome Overview ...... 5
1.4 Summary of Current EA WFD Data ...... 6
2.0 Methodology ...... 7
2.1 Point and Diffuse Pollution Sources ...... 8
2.2 Barriers to Fish Migration ...... 8
2.3 Personnel ...... 8
3.0 Results ...... 8
3.1 Overview ...... 9
3.2 Grade 1 Sources ...... 11
3.3 Grade 2 Sources ...... 14
4.0 Discussion...... 19
4.1 Point Sources...... 19
4.2 Diffuse Sources...... 19
4.3 Barriers to Fish Migration and Connectivity ...... 19
5.0 Conclusions and Recommendations ...... 20
6.0 References ...... 22
Bristol and Avon Rivers Trust 1 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd 7.0 Appendices ...... 23
Appendix 1 – Table. 1: Tiers 1 and 2 descriptions with associated categories and codes ...... 23
Appendix 2 – Grade Maps...... 28
Appendix 3 – Source Type Maps ...... 46
Appendix 4 – Field Data Sheet / Land Use Codes ...... 58
Bristol and Avon Rivers Trust 2 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd Executive Summary
In 2014, Ahern Ecology Ltd. was commissioned by Bristol and Avon Rivers Trust (BART) to undertake a Catchment Walkover Survey of the Somerset Frome. The purpose of the survey was to utilise a catchment-scale methodology to simultaneously identify and classify diffuse and point inputs of phosphates, ammonia, other pollutants in addition to barriers to fish migration within the waterbody, between Rode and Witham Friary. The 3-day catchment walkover survey encompassed 19km of the River Frome, assessing all active and potential issues within three Water Framework Directive (WFD) sub-waterbodies (GB109053021840, GB109053022120 and GB109053022080). The main pressures identified by the current River Basin Management Plan (RBMP), are agricultural diffuse pollution, intermittent urban discharges, abstraction and invasive non-native species. Furthermore, the current 2013 WFD ecological classification highlights that the Somerset Frome does not, at present, provide suitable conditions for fish to meet Good Ecological Status (GES). The physico-chemical quality of the Frome is generally good and macroinvertebrates are consistently classified as ‘High’. The WFD classifications indicate that excess phosphate is a persistent pressure in the upper reaches of the Frome. This is not surprising, due to the predominantly rural nature and prevalence of agricultural land uses around the area of Witham Friary, up to the outskirts of the urban conurbation of Frome. Disruption to catchment connectivity by manmade and natural barriers is indicated by the WFD classifications, resulting in ‘Moderate’ to ‘Poor’ fish status within these three reaches of the River Frome. A total of 156 sources were recorded, 3 were Grade 1, 17 were Grade 2, 83 were Grade 3 and 51 were classified as having the potential to cause an input of diffuse or point source pollution into the River Frome. Point sources were more frequent (109 sources) than diffuse sources (48). Lack of connectivity was confirmed by the catchment walkover surveys, which found that weirs were the dominant recorded issue (19 sources). Frequent examples of urban intermittent discharges from domestic and residential premises (17 sources) and transport links (11 sources) were also identified. Agricultural diffuse pollution such as run-off from over-wintering pads, poaching and pathways around farm tracks resulting in more severe Grade 2 inputs, were more commonly encountered in the upper reaches of the River Frome.
The connectivity issues facing catchment and river managers on the River Frome are highly complex and potential solutions for the majority of larger scale weirs are likely to be ‘disproportionately expensive’. The feasibility of installing fish passes or removing smaller barriers to fish migration requires further detailed investigation.
Although phosphate levels in the River Frome between Witham Friary and Rode are unlikely to reach GES by 2015. Participation in capital grant schemes, such as the Egford Borehole, will allow landowners to install watercourse fencing, hard bases for livestock drinkers and ram pumps (Natural England 2014). A subsequent reduction in levels of diffuse agricultural pollution arising from livestock and arable farming should be seen catchment wide as a result.
Bristol and Avon Rivers Trust 3 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd 1.0 Introduction In 2014, Ahern Ecology Ltd. was commissioned by Bristol and Avon Rivers Trust (BART) to undertake a Catchment Walkover Survey of the Somerset Frome. The purpose of the survey was to utilise a catchment-scale methodology to simultaneously identify and classify diffuse and point inputs of phosphates, ammonia and other pollutants within the Somerset Frome waterbody, between Rode and Witham Friary. In addition, any barriers to fish migration identified on the main channel were assessed and classified.
1.1 Background
In March 2011, the Coalition Government announced their commitment to the catchment approach for delivering sustainable, cost-effective environmental improvement schemes for the benefit of both the environment and society. At the heart of this approach is the practice of catchment scale decision- making, with stakeholders working together to deliver actions locally. Over the next four years, £92 million will be available through the Catchment Restoration Fund (CRF) to improve the health of the UK’s rivers, lakes and estuaries. In 2011/2012, £18 million of this funding was provided to the Environment Agency, Natural England, The Wildlife Trusts, The Rivers Trust, the Non-native Invasive Species Secretariat and Local Actions groups, in order to deliver projects aimed at achieving Good Status (GS) in all waterbodies under the Water Framework Directive 2000/60/EC (WFD) by 2015. The aims of the catchment approach include restoring old river courses, aiding fish migration, increasing channel width, removing silt, increasing water retention and halting the spread of invasive non-native species (INNS). A pivotal factor causing a significant number of waterbodies to fail WFD targets is diffuse pollution. Agricultural activities are not the sole causes of diffuse pollution, however, these types of land-use contribute to approximately 60% of nitrates, 25% of phosphorous and 70% of sediments entering UK watercourses (DEFRA 2008). The catchment approach seeks to understand, pinpoint and reduce sources of rural diffuse pollution causing deterioration in water quality, degradation of fish and spawning habitat and reduction in overall ecological quality.
The focus of this survey is the identification of sources of nutrient pollution, sediment and barriers to migration, and not the specific environmental fate and ecological consequences of theses sources. By identifying key inputs of pollution in the Somerset Frome, this will provide a robust evidence base to support catchment delivery at the local scale.
1.1.1 Water Framework Directive (2000/60/EC)
The Water Framework Directive (2000/60/EC) came into force in December 2000 and subsequently became part of UK law in December 2003. The legislation is designed to improve and integrate the manner in which waterbodies are managed. Furthermore, it aims to enhance the status and prevent further deterioration of aquatic ecosystems, promote the sustainable use of water, reduce pollution of water by ‘priority’ and ‘priority hazardous’ substances and ensure progressive reduction of groundwater
Bristol and Avon Rivers Trust 4 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd pollution. All member states must aim to reach good chemical and ecological status in both inland and coastal waters by 2015. Despite this, in England and Wales only 26% of waterbodies achieved ‘good status’ in 2009 (CAONB 2012). The WFD waterbody condition assessments are currently undertaken by the Environment Agency using methodologies agreed with the UK Technical Advisory Group (UK TAG). For surface waters, such as rivers and lakes, the ‘overall status’ of a waterbody is comprised of an ecological and a chemical component. Ecological status is recorded on the scale high, good, moderate, poor and bad (with moderate or worse being regarded as a failure), while chemical status is measured simply as ‘good’ or ‘fail’. Recommendations for remedial catchment management interventions are made through River Basin Managements Plans (RBMPs) and Catchment Management Plans (CMPs). The Bristol Avon and North Somerset Streams is one of DEFRA’s 25 catchment pilots, hosted by the Avon Frome Partnership and covering the Bristol Avon and North Somerset Streams management catchment. The pilot sought to understand catchment functionality and the ways in which stakeholders operate within it. The current RBMP, encompassing the Somerset Frome, identifies urban intermittent discharges, such as sewage treatment works, invasive non-native species (INNS), abstraction and agricultural diffuse pollution as the main challenges facing these catchments (EA 2009). The plan promotes adaptive and collaborative approaches, which include ‘Operation Streamclean’, a partnership project with Wessex Water to highlight and correct sewerage misconnections, Catchment Sensitive Farming (CSF) delivery initiatives (such as the Egford Borehole), the Avon Frome Partnership and Bristol Invasive Weeds Forum to tackle these issues.
1.2 Somerset Frome Overview
The Somerset Frome flows for approximately 34 km from its source near Bungalow Farm, Cannwood to its confluence with the River Avon at Freshford. Flowing in a north easterly direction towards Witham Friary, smaller tributaries formed in Marston Wood and Little Bradley join the Frome to the east, with tributaries from Trudoxhill meeting the river from the west. The Frome flows adjacent to Blatchbridge, through Frome town centre, where the Mells River joins at Spring Gardens. The river continues in a north easterly direction, flowing past Oldford and Beckington where it is joined by Henhambridge Brook. The Frome flows to the east of Rode, through Tellisford and north towards Farleigh Hungerford.
The hydrogeology of the Frome catchment is comprised of a significant limestone aquifer (Great Oolite Group) capable of producing large yields and a flashy response to precipitation. To the south east of the catchment, the hydrogeology is predominantly poorly drained Oxford Clay.
Several Sites of Special Scientific Interest (SSSI) are located within the Somerset Frome catchment. These include Postlebury Wood SSSI (an 86 hectare broadleaved woodland) located north of Witham Friary, Vallis Vale SSSI located around Mells Stream and Longleat Woods SSSI (223 hectares of broadleaved woodland).
The upper reaches of the Somerset Frome have the potential to provide good juvenile and parr Brown Trout (Salmo trutta) habitat, with suitable riffle and backwater sections. The Mells River provides good
Bristol and Avon Rivers Trust 5 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd adult Brown Trout habitat. The lower reaches of the Somerset Frome provide more suitable habitat for coarse fish, such as chub (Squalius cephalus), roach (Rutilus rutilus) and dace (Leuciscus leuciscus).
1.3 Summary of Current EA WFD Data
For the purposes of this walkover survey and report, the walkover reach has been split into three sections following the WFD waterbody classification and identification scheme. The most downstream section (GB109053021840) is referred to as the Frome – confluence of River Mells to confluence of River Avon, the intermediary section is referred to as the Frome – confluence of Rodden Brook to confluence of River Mells (GB109053022120) and the upper most section is referred to as the Frome – source to confluence of Maiden Bradley Brook (GB109053022080).
The current ecological and physico-chemical WFD classifications for these reaches are summarised below (Table 1). The uppermost reach is not designated a heavily modified waterbody and the overall status is classified as ‘Poor’. The ‘Poor’ classification is led by the fish biological element, which is predicted to rise to ‘Moderate’ status by 2015. It has been determined that it would be ‘disproportionately expensive’ to try and achieve GES by 2015 (EA 2009). The upstream reach of the River Frome, therefore has only 30% of the expected fish species present and >30% of the expected abundance. Reduction in diversity and abundance can be due to a number of varying factors, such as unsuitable habitat, poor water quality, unsustainable or poor macroinvertebrate communities and lack of connectivity. However, the hydrology and morphology of the River Frome near its source have been classified as ‘High’ and ‘Good’ respectively, indicating that suitable habitat should exist for a variety of fish species. In addition, dissolved oxygen and pH meet or exceed GES, suggesting that these physico- chemical indicators are not contributing factors in the reduction of fish biological quality in the reach. A diverse and highly scoring community of macroinvertebrates are available as a food source. Thus, the absence of connectivity in the reach is the overriding factor causing declines in fish populations and subsequent diversity. The connectivity of the River Frome, to the confluence with Maiden Bradley Brook, is currently being affected by natural and man-made barriers, such as large woody debris (LWD), weirs and dams, which impede the natural passage of fish. Large barriers can have a major impact on fish population numbers and diversity, as feeding or spawning movements upstream or downstream of the obstruction are prevented. Ammonia and phosphate levels do not meet GES, suggesting that rural diffuse pollution is an additional pressure on both water and biological quality in this reach.
Slight improvements in ecological and physico-chemical quality are seen in the intermediary and downstream reaches of the River Frome. All water quality indicators meet GES, except phosphate. There is a reduction in the ammonia pressure as the River Frome flows through increasingly urbanised areas and away from rural land use influences. Dissolved oxygen also improves and remains at ‘High’ status until the confluence with the River Avon. Downstream from the confluence with Rodden Brook, the River Frome is designated as a Heavily Modified Waterbody (HMWB), where sections through the urban conurbation of Frome have been significantly engineered and hydrological characteristics have been altered. The ecological quality returns to ‘Poor’ status in the final reach, due to unsatisfactory fish
Bristol and Avon Rivers Trust 6 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd biological quality. Once again, the ‘Good’ chemical status and ‘High’ macroinvertebrate quality suggests that the fish failure is due to a lack of connectivity and a disruption to fish mobility in the catchment.
Table 1 Summary of EA WFD Waterbody classification data for the three surveyed reaches of the River Frome
Waterbody Name R Frome – source to conf R Frome – conf Rodden Frome - conf R Mells to Maiden Bradley Bk Bk to conf Mells R conf R Avon (Brist) Waterbody ID GB109053022080 GB109053022120 GB109053021840 Low, Small, Calcareous Low, Small, Calcareous Low, Medium, Calcareous Typology (Not designated A Heavily (Heavily modified) (Heavily modified) Modified Waterbody) Overall Status Poor Moderate Poor Ecological Status Poor Moderate Poor Chemical Status X X Good Biological Fish Poor X Poor Macroinvertebrates High High High Physico-chemical Ammonia Moderate Good High Dissolved Oxygen Good High High pH High High High Phosphate Moderate Moderate Moderate Hydromorphology Hydrology High Not High Not High Morphology Good X Good
2.0 Methodology
A standardised 3-day baseline walkover survey of a 19 km stretch of the River Frome in Somerset was
undertaken by a team of Ahern Ecology Ltd. Aquatic Ecologists during April 2014. The reaches
surveyed are provided in Table. 2 below. Walking in a downstream to upstream direction, each reach
was walked by two ecologists for accuracy and health and safety reasons.
Table 2 Surveyed reaches of the River Frome, Somerset
Reach NGR Start Point NGR End Point Date Surveyed Reach Length (km)
1 ST8021854321 ST7858550571 02/04/2014 5.6
2 ST7858550571 ST7864546570 03/04/2014 4.2
3 ST7864546570 ST7864546570 04/04/2014 8.8
Bristol and Avon Rivers Trust 7 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd 2.1 Point and Diffuse Pollution Sources
Diffuse and point sources of pollution entering the waterbody, including sediment and organic inputs,
were identified and recorded on the survey form (Appendix 4). Each source was categorised based on
the EA standard walkover survey methodology OI 356_12 (Appendix 1: Table 1) and the location
recorded as a 10 figure National Grid Reference (NGR) using a hand-held GPS, to allow subsequent
spatial distribution analysis through ArcGIS. The origin of each input was recorded to facilitate analysis
into the types of land-use practices causing significant levels of pollution into the catchment as a whole.
The impact or potential severity of each source was classified on a scale of Grade 1 to Grade 4
(Appendix 2). Photographs were taken of each source and relevant comments recorded as appropriate.
Additional information recorded included the type of land-use on both banks (Appendix 4: Table 1) and
whether stock fencing was present.
2.2 Barriers to Fish Migration
Any natural and manmade barriers to fish migration, such as LWD, weirs, dams and fords, were also
recorded and assessed using EA standard walkover methodology. The type, length, width and degree
of influence of the barrier were recorded, with the passability assessed from Grade 1 to Grade 4
(Appendix 2).
2.3 Personnel
The surveys were undertaken by: . Rachel Whatmore ACIEEM . Adam Ellis MCIEEM . Jessy Grant MCIEEM . Simon Browning (Wavelength Environmental)
3.0 Results
In this section, an overview of the issues recorded on the River Frome is presented. Individual sources of note are described and discussed.
It is intended that this information will provide a comprehensive picture of the main factors that are contributing to the River Frome failing to achieve GES and allow potential restoration measures to be identified and devised.
Bristol and Avon Rivers Trust 8 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd 3.1 Overview
A total of 156 sources were recorded on the 19 km walked between Rode and Witham Friary. Of these, 48 were diffuse and 109 were point sources. In addition, 2 ungraded points of interested were noted, which were small abstractions. The source grade analysis is shown in Figure 1. The majority of sources were classified as Grade 3, with a total of 83 inputs. A third of sources (51) were recorded as potential inputs. Three Grade 1 sources (2%) and 17 Grade 2 sources (11%) were recorded on the River Frome. Figure 1: Percentage of sources analysed by Grade
Percentage of sources by Grade 1% 2%
11%
33%
53%
1 2 3 4 Other
The location of each source has been mapped in ArcGIS (Appendix 2). An analysis of graded sources by category (Figure 2), highlights the groups of activities and issues causing notable inputs of sediment or pollution and causing severe disruptions to fish movement. All Grade 1 sources were classified as Category E (others) and recorded as significant barriers to fish migration (BAR-WE). Livestock (Category B) and other sources (Category E) were the sole contributors to Grade 2 sources on the River Frome, with 1 and 16 sources respectively. Other sources (Category E) were the largest cause of Grade 3 inputs/issues, with a total number of 45 recorded. Point source conduits (Category C), accounted for 42% of Grade 3 pollution inputs into the River Frome. Similarly, inactive conduits and pipes accounted for almost half (47%) of the potential sources of pollution input. Anthropogenic or industrial and other sources each contribute 16% of the potential sources recorded.
Bristol and Avon Rivers Trust 9 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd
Analysis of graded sources by category
50 45 40 35 30 25 20 15 10 5
0
Number of Sources per Category per Sources of Number
A - - Arable A - Arable A
E - - Others E - Others E - Others E - Others E
C - Conduits - C Conduits - C
B - - Livestock B - Livestock B - Livestock B
D - Anthropogenic - D Anthropogenic - D
1 2 3 4
Grade / Category
Figure 2: Number of sources per Grade and analysed by Category
A total of 21 different types of pollution sources or potential issues were documented during the catchment walkover survey. These are mapped separately in Appendix 3. The most common type of
Number of Sources per Type 20 19 18 17 16 15 14 13 12 12 11 10 9 9 9 8 8 7 7 Source 6 5 4 Type 4 3 3
NumberofSourcesRecorded 2 1 1 1 1 1 0
Source Type
Figure 3: Number of sources per type
Bristol and Avon Rivers Trust 10 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd issue recorded (12%) were barriers to fish migration; specifically weirs (BAR-WE) (Figure 3). In addition, natural barriers were also numerous with 13 separate agglomerations of large woody debris completely obscuring fish passage noted. Pipes from unidentified sources or premises accounted for 11% of the source types and domestic or residential pipes accounting for a further 10%. Pipes derived from agricultural or transport sources were recorded slightly less frequently, at 8% and 7% respectively. The most frequent type of diffuse pollution encountered was general poaching (6%), followed by erosion and overland flow; each accounting for 5% of sources recorded. Evidence of fly-tipping was noted on 9 separate occasions. Sources originating from gulleys, forestry felling operations, water industry pipes and unspecified drainage ditches were the least common. No INNS were recorded during the survey, due to the time of year the walkover was conducted.
3.2 Grade 1 Sources
Three Grade 1 sources were recorded on the River Frome between Rode and Witham Friary. Individual Grade 1 assessments were completed for each source.
Table 3 Grade 1 Sheet for source 44
Project 1667 River Somerset Frome
Site Number 44 Recorder RW
Date 02/04/2014 NGR ST7876551570
Category E Type BAR-WE
Description Stepped weir approximately 4m high and 20m wide.
Land use LHB: IG – Improved / semi-improved RHB: Suburban / urban development
grassland
Comments A curved stepped weir of approximately 4m in height and 20m in width, at The Mill
House, Lullington. The weir might only be passable for migratory fish species in
exceptionally high flows. A 90kw Archimedes Screw turbine has been installed at
The Mill House.
Bristol and Avon Rivers Trust 11 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd
The first Grade 1 barrier was recorded at the 18th century The Mill House on Lullington Lane (ST7876551570) (Table 3). The weir is transverse across the channel and is stepped to create a cascade during low flows. The head-loss is approximately 4m and appears to be more gently sloping on the right-hand bank (RHB) due to a slight compound area directing the majority of the flow. The RHB directly downstream of the weir has been scoured and presents a significant sediment loading potential during high flows. The weir is impassable to the majority of fish species and disrupts the connectivity between upstream and downstream populations. Discernible backwater effects were noted for approximately 800m upstream of the weir, where the reach had become impounded, the flow reduced and sedimentation had increased. Loss of flow is also likely to affect the diversity and abundance of fish populations upstream of the Mill House weir.
Table 4 Grade 1 sheet for source 62
Project 1667 River Somerset Frome
Site Number 62 Recorder RW
Date 03/04/2014 NGR ST7726049542
Category E Type BAR-WE
Description Curved weir approximately 4m high and 35m wide.
Land use LHB: RP – Rough unimproved RHB: SU - Suburban / urban development
grassland / pasture
Comments Large curved weir, causing significant impoundment upstream and reduction in flow.
The barrier would only be passable by migratory fish in exceptionally high flows.
Bristol and Avon Rivers Trust 12 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd
Source 62 (Table 4) is a very large curved weir, approximately 35m in length with a slightly aerated nappe and head loss of 4m. The weir would be impassable for most migratory fish species, except in flows which reduce the water head. The reach upstream of the weir is significantly impounded and the flow reduced. Flood debris, such as tree trunks and logs, were noted on the crest of the weir. Reductions in flow and increased sedimentation have altered the habitat, evidenced by the growth of yellow water- lily (Nuphar lutea) and macrophytes commonly encountered in lentic ecosystems in the backwaters of the weir.
Table 5 Grade 1 sheet for source 110
Project 1667 River Somerset Frome
Site Number 110 Recorder RW
Date 04/04/2014 NGR ST7762145678
Category E Type BAR-WE
Description Weir approximately 3m high and 5m wide.
Land use LHB: IG – Improved / semi-improved RHB: IG – Improved / semi-improved
grassland grassland
Comments Blatchbridge Mill Weir with attached sluice gate.
Bristol and Avon Rivers Trust 13 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd
Blatchbridge Mill Weir (source 110) (Table 5) is located at ST7762145678 adjacent to the disused mill house. The weir is broad-crested and transverse with an attached sluice gate on the RHB. The width is relatively small, at 5m, however the headloss is approximately 3m and steeply inclined. The weir is completely impassable to migratory fish species.
3.3 Grade 2 Sources
A further 10 barriers (9 weirs and 1 groyne) were classified as Grade 2 during the walkover survey. Five of these barriers (sources 20, 26, 27, 30 and 34) were located within a 1.34 km reach of the River Frome.
Notably, 35% of the Grade 2 sources are located in the upstream waterbody (GB109053022080) and originate from rural or agricultural land uses and activities. Four sources, in particular, were assessed as having the potential to cause significant inputs of ammonia and phosphate into the River Frome. Firstly, a ditch running alongside Vinney Lane at ST7737245579 had a strong sewage odour and there was evidence of sewage fungus (Figure 4). The pollution appeared to originate from temporary dwellings and a construction site on Vinney Lane.
Bristol and Avon Rivers Trust 14 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd
Figure 4: Source 111 - Ditch alongside Vinney Lane flowing into a tributary of the River Frome. The ditch is blocked with sediment. There was evidence of sewage fungus growth and a strong sewage odour (Photo IDs 737-738).
Bristol and Avon Rivers Trust 15 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd Evidence of overland run-off from overwintering pads at Bullridge Farm (ST7756344562) was recorded and classified as a Grade 2 source (source 118). The gentle incline of the grassy area adjacent to the river had resulted in an enriched pool, comprised of slurry, hay and sediment to form (Figure 5). There was a strong odour of sewage and slurry. Connecting pathways to the River Frome had formed and during rainfall events this source may have discernible ammonia and phosphate loading potential. No sewage fungus was recorded downstream of these pathways. Bundles of garden waste appeared to have been placed on top of the pool of slurry.
Bristol and Avon Rivers Trust 16 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd
Figure 5: Source 118 - Large pool of accumulated slurry material with algal and bacterial growths from overwintering pads on Bullridge Farm. Overland run-off pathways into the River Frome (Photo IDs 746-748).
A plume of sediment from an unnamed tributary was recorded at ST7623242716 (source 139), in addition to a strong corresponding sewage odour (Figure 6). The mixing zone, circled in red, extended approximately 2m upstream. The tributary was discharging into the River Frome at a fast rate and appeared to flow for 320m from a copse south of Foghamshire Lane. To determine the origins and severity of the pollution source further investigation is required. On the day the pollution input was recorded, there had not been any antecedent precipitation suggesting the plume was being actively discharged from source.
Bristol and Avon Rivers Trust 17 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd
Figure 6: Source 139 – A plume of green/brown highly turbid discharge from an unknown tributary flowing from a copse south of Foghamshire Lane.
The most severe example of livestock poaching was recorded at ST7811046099 (Figure 7). A large number of horses appear to have access to the river for drinking water, due to broken stock fencing and poached banks. The slope incline and bare sediment presents a significant diffuse pollution potential. The loss of riparian vegetation has caused and worsened bank instability, which can have a direct affect on fish spawning and feeding due to siltation of the bed substrate. The eroded sediment may also serve to transport excess nutrients and faecal contaminants from manure.
Figure 7: Source 107 – Poaching and bank erosion caused by livestock (horses) trampling (Photo IDs 730-731).
Bristol and Avon Rivers Trust 18 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd 4.0 Discussion
4.1 Point Sources
The catchment walkover survey confirmed the conclusions of the RBMP, whereby urban intermittent discharges present one of the most significant pressures on Severn Basin Catchments. Conduits and pipes originating from agricultural premises or drainage ditches were also frequent and therefore pose a notable phosphate loading potential. Due to the rural nature of the catchment, many of the unidentified point source pipe inputs (PS-PNI) are likely to originate from septic tanks and private sewage treatment plants. Failing or misconnected systems may be contributing to the failing of the River Frome to meet GES for phosphate. A supplementary wet-weather survey may be beneficial to determine the severity of a number of Grade 4 point source inputs, which were inactive during the baseline catchment walkover.
4.2 Diffuse Sources
Diffuse pollution inputs into the River Frome were far less numerous than point sources. Poaching and erosion were the most significant pressures identified during the survey and these sources are commonly connected. The flashy nature of the watercourse has resulted in a number of undercut banks and recent bank slips. The input of excess sediment and fine material has the potential to smother fish spawning habitat. To reduce bank erosion and riparian vegetation degradation by livestock, designated cattle drinkers are recommended where mains water supply is not possible. River gates can prevent cattle moving along the channel in crossing areas. Hard-standing surface around supplementary feeding stations will reduce the impact of poaching. The preference is to site feeders away from the watercourse. Landowners may seek to explore other drinking systems such as nose operated pasture pumps, or solar power pumps. Such measures will reduce soil erosion and help to prevent siltation of spawning gravels and bed substrate. Restricting livestock from the watercourse will also reduce the ammonia and phosphate loading potential. Phosphate can be reduced by the interception of surface and ditch water entering the watercourse by the creation of silt traps. Although there were examples of ‘good practice’ along the River Frome, increasing the existence of riparian buffer strips between intensively managed agricultural land and the watercourse will serve to trap silt and filter nutrient loading. By working with landowners and managers, soil plans can be created which will allow areas prone to soil erosion to be mapped and aid the targeted application of fertilisers.
4.3 Barriers to Fish Migration and Connectivity
The number and scale of barriers present on the River Frome between Witham Friary and Rode, present a significant issue to the successful catchment management and delivery of WFD objectives. Barriers to migratory fish movement have been created in all cases due to changes in hydraulic conditions at the structures, which exceed the swimming capabilities or do not suit the behavioural characteristics of fish attempting to pass upstream. The major changes to natural waterway conditions
Bristol and Avon Rivers Trust 19 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd at these sites include, higher velocities, reduced flow depth, lack of resting places or shelter, excess turbulence and water surface drop. The manmade barriers such as weirs, fords and groynes require investigation on a case-by-case base. There may be scope for retrofitting fish migratory aids, such as fish ladders and passes, on a number of structures on the River Frome. A large number of LWD dams were recorded during the walkover survey. Woody debris can provide refugia from high velocity flows, shade, feeding, spawning and nursery habitat for a number of fish, macroinvertebrate and mammalian species. However, where the location of LWD is deemed to be causing locally high water levels, hydraulic investigation should be conducted prior to any removal works.
5.0 Conclusions and Recommendations
The 3-day baseline catchment walkover survey of the River Frome, covering 19km between Witham Friary and Rode identified 156 sources or issues affecting the successful achievement of WFD objectives and GES by 2015. The waterbody is currently classified as having good physico-chemical and macroinvertebrate statuses. The main pressures identified were the number and scale of manmade barriers, effectively disrupting connectivity and reducing fish migration. This has led to a ‘Poor’ fish classification in the upper most reach of the River Frome and the reach between Frome and the confluence with the River Avon. Intermittent urban and agricultural conduits require further investigation and targeted wet-weather sampling, to elucidate source origins and pollution severity. Targeted remedial measures in the upper reaches of the River Frome, aimed at reducing diffuse agricultural pollution from livestock, are likely to improve the current ‘Moderate’ phosphate status.
A series of recommendations can be made following the analysis of the catchment walkover data:
Stock fencing should be improved and buffer strips considered in the reaches around Shawford, Dairy House Farm, Southfield Farm and Lower Marsh Farm, to prevent over-grazing, poaching and input of excess sediment and nutrients into the River Frome. Further investigations should be carried out on the River Frome downstream of Rode to the confluence of the River Avon. In addition, numerous tributaries outside the scope of this study such as the River Mells, Wheel Brook, Hardington Brook, Buckland Brook, Egford Brook, Fordbury Water, Redford Water and Marston Brook, also warrant investigation to provide a comprehensive picture of catchment wide pollution and migration barrier issues. Accumulations of LWD should be reviewed on a case-by-case basis and may warrant further investigation utilising River Habitat Surveys (RHS) and River Corridor Surveys (RCS) to determine which debris dams are advantageous to the Frome’s ecological quality and those which pose threats of localised flooding. The source discharging from an unidentified tributary, at ST7623242716, requires further investigation using water quality monitoring techniques. In addition to an in-depth walkover of this reach, water quality samples should be taken upstream, downstream and at selected points on the tributary to pinpoint the exact source of the pollution input. A water quality SONDE could
Bristol and Avon Rivers Trust 20 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd be deployed downstream of the pollution input, in order to monitor the temporal nature of the discharge. Liaison with riparian landowners may be advantageous to prevent further deposition of natural and manmade materials on within the riparian zone. Stock fencing should be improved and buffer strips considered in the reaches around Shawford, Dairy House Farm, Southfield Farm and Lower Marsh Farm, to prevent over-grazing, poaching and input of excess sediment and nutrients into the River Frome. Conducting a follow up wet-weather survey will allow the determination of the severity and origin of a number of Grade 4 sources recorded during the baseline catchment walkover.
Bristol and Avon Rivers Trust 21 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd 6.0 References Commented [AE2]: Delete as appropriate
APEM (2010) A field guide to the classification of fine sediment sources in river catchments: A tool developed by APEM Ltd. in collaboration with the Environment Agency (EA).
CAONB (2012) Water Framework Directive Catchments and Catchment Sensitive Farming. Available at: http://www.cotswoldsaonb.org.uk/userfiles/file/meetings-2012/c-and-m/item-7-water-framework- directive-catchments-and-catchment-sensitive-farming.pdf (Accessed on: 10/05/2014).
DEFRA (2008) Catchment Sensitive Farming. Information on the On-going Review of the Catchment Sensitive Farming Programme.
DEFRA (2013) Catchment Based Approach: Improving the quality of our water environment. Available at: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/204231/pb13934- water-environment-catchment-based-approach.pdf (Accessed on: 11/05/2014).
EA (2009) River Basin Management Plan: Severn River Basin District. Available at:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/291442/gemi0910bssk-
e-e.pdf (Accessed on: 09/05/2014).
Natural England (2014) Capital Grant Scheme – Funding Priority Statement. Catchment 65: Egford
Borehole 2014/15.
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7.0 Appendices
Appendix 1 – Table. 1: Tiers 1 and 2 descriptions with associated categories and codes
Tier 1 Tier 2 Category Code
Cultivation right up to banks (No Buffer zones or field margins) A BUF
Gulleying and soil erosion A GUL
Arable field Soil compaction and run-off A COM
Soil wash A WAS
Rills and soil erosion A RIL
Field organic manure (livestock & biowaste) heap A FYM
Farm activity Landspreading of organic manure (livestock, sewage sludge or industrial) - record whether surface or sub-surface A SPR application in comments
Farmyard run-off B FYR
Farm infrastructure Farm tracks & gateways (as pathways) B FTG
Leaking silage clamps B SIL
Leaking field silage and compressed bales B FSB
Bristol and Avon Rivers Trust 23 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd Leaking slurry/biowaste store B SLU
Soak-aways – slurry B SOA
Leaking fuel store B FUE
Mobile sheep dipping area B MSH
Static sheep dip B SSH
Pesticide store, mixing & handling area B PES
Out-wintering pads (OWPs) B OWP
Poaching around feeding and watering stations B POA
Livestock field General poaching and trampling B POT
Bank erosion related to over-grazing B BNK
Pipe/Run-off – Transport – Road C PS - TRSr
Urban and Point (including Site Run-off - Service sector – Construction/demolition C RO- SScon surface water drainage Domestic and residential - Septic Tanks and Cesspits D PS-DRst pipes) STW - Domestic and residential D PS-DRstw
STW - Water Industry D PS-WIstw
CSO - Water Industry D PS-WIcso
Bristol and Avon Rivers Trust 24 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd Pipe – Farm (including field drains) A PS-Ag
Pipe – Manufacturing D PS-MAN
Pipe - Power Generation and Supply D PS-PGS
Pipe - Premises type not identified C PS-PNI
Pipe - Domestic & residential (inc. Misconnections) D PS-DR Urban and Point (including Pipe - Retail Sector D PS-RS surface water drainage Pipe - Service sector D PS-SS pipes) Pipe - Transport – Rail, Air or Other Transport (cargo handling, marinas, pipeline) – excluding Road (see above) D PS-TRSoth (continued) Pipe - Water Industry (e.g. potable water supply/treatment) D PS-WI
Pipe - Waste Management -Transfer station, landfill etc. D PS-WM
Land use within 50 m of bank top (record significant changes in predominant land use) D Text box
Waterfall E WFL
Hydro-morphological Significant large-scale woody debris prohibiting passage* E LWD
Condition Manmade barrier – Weirs, sluices or dam across river channel E BAR – We
Manmade barrier – Culverts E BAR – Cul
Manmade barrier – Bridges E BAR – Bri
Bristol and Avon Rivers Trust 25 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd Manmade barrier – Outfalls/Intakes E BAR – Dis
Manmade barrier – Fords E BAR – For
Manmade barrier – Deflectors/groynes/croys E BAR – Gro
Manmade barrier – Other significant man-made influence or engineering structure (specify in text) E BAR – Oth
Erosional features (record in text box = eroding cliff, stable cliff, exposed bedrock & boulders) E ERO + text
Depositional feature (record in text box = mid-channel bars, islands, side bars and point bars) E DEP + text
Tree cover (pick-list = isolated, regularly spaced/single, occasional clumps, semi-continuous, continuous) E Pick-list
Forestry drain connection to watercourse E FDR
Forestry ground preparation E RBZ
Forestry plantation Forestry felling operations E FGP
Forestry Leaking fuel stores E FFO
Forestry Road and track run-off E FSS
Japanese Knotweed E JKW INNS Himalayan Balsam E HIM
Giant Hogweed E HOG
Floating Pennywort E FLP
Bristol and Avon Rivers Trust 26 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd Run-off – not via drain/pipe i.e. overland flow direct to watercourse – specify NIRs tier 1 sector in comments e.g. E ORO Premises type not specified
Pipe/Run-off - Natural sources - Abandon mines E NS - Am
Dredging E DRE
Fly tipping E FLY Other Issues Drainage ditch – unspecified premises E ODD
closed forest canopy E CFC
Pipe/Run-off - Natural sources - Contaminated land E NS - ConL
Pipe/Run-off - Contaminated in-situ sediment E SED
Other Source (specify in comments) E OS
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Appendix 2 – Grade Maps
Key
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Bristol and Avon Rivers Trust 45 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd Appendix 3 – Source Type Maps
Key
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Bristol and Avon Rivers Trust 57 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd Appendix 4 – Field Data Sheet / Land Use Codes
Bristol and Avon Rivers Trust 58 June 2014 Somerset Frome Catchment Walkover Report Ahern Ecology Ltd Key to Land Use Abbreviations (from APEM 2010)
Code Land use Description
BL Broadleaved or mixed woodland (semi-natural)
BP Broadleaved or mixed plantation
CW Coniferous woodland (semi-natural)
CP Coniferous plantation
WW Wet woodland
SH Scrub and shrubs
OR Orchard
WL Wetland (e.g. bog, marsh or fen)
MH Moorland / heath
AW Artificial open water
OW Natural open water
RP Rough unimproved grassland / pasture
IG Improved / semi-improved grassland
TH Tall herbs and rank vegetation
RD Rock, scree or sand dunes
SU Sub-urban or urban development
TL Tilled land
IL Irrigated land
PG Parkland or gardens
NV Not visible
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