Page 1

Avon Sediment Pathways report The aim of this report is to describe and summarise the findings of the wet weather walkover surveys undertaken for specific sub-catchments identified as a ‘High’ priority as part of the Hampshire Avon Catchment Partnerships Sediment Pathways Project. Actual and likely sediment pathways in the selected ‘High’ priority sub catchments have been logged and the details of the source recorded so that mitigation can be put in place, either through existing projects and partners operating within the catchment or with the help of bespoke advice from others. The initial desktop survey brought together 7 different sets of data to build a combined Risk Map for the whole of the Hampshire Avon Catchment. The risk map has ensured that the limited amount of resources for this project were spent on higher risk areas. The datasets used were collated from free resources, which reduced the final resolution and how up to date the final risk map is. Commercially available datasets can be used to upgrade the resolution and age of the data, but at a substantial cost. The 7 data sets used were: 1. Met office Annual average rainfall – The greater the rainfall the greater the likelihood of overland flow pathways developing 2. EA Phosphate classification failure 2014 data – WFD failure for phosphate within a sub catchment can be as a result of high levels of sediment ingress into the channel, pinpointing catchments that require intervention. 3. OS Landforms Dominant Slope data – Fields with steeper slopes can generate water run-off and thus increase the likelihood that sediment will be mobilised from them. Highest risk fields are generally considered to be those with an angle over 70 (EA Think Soils Handbook). 4. EU Soils - Soil erodibility data – The greater the risk of soil erosion due to increased run-off needs to be considered when assessing the mobilisation of sediments overland. 5. Corine Landcover 2007 field use data – Some agricultural practices are a greater risk to sediment being transferred by overland pathways than others. Land tilled for arable cultivation or short term grassland poses more of a risk than long term and natural grasslands/Pasture. 6. BGS Geology data – The natural texture wetness and structure of geological typology have a very strong effect on ability of the land to regulate the movement of water and its likelihood to pose a risk to water quality. 7. Field boundaries in close proximity to watercourses - If not undertaken according to good practice, land management can represent a risk to water quality in neighbouring watercourses. Furthermore the land practices and other characteristics can act to elevate the level of risk from overland flow. Once each dataset was mapped, a risk score was attached to the different map attributes. A higher risk score was given to an attribute that has a greater potential to create or support the creation of sediment pathways overland. Once each dataset was mapped individually they were brought together into a combined risk map (fig.1). The map shows the risk placed on the occurrence of sediment pathways through overland flow within the whole of the Hampshire Avon catchment with the most vulnerable areas concentrated in the Upper Avon, Upper Wylye and Upper Nadder Catchments. These high risk areas directed the focus of the wet weather walkover surveys. Outputs from an earlier walkover survey by APEM (2010) was also used to help pinpoint catchments with historic issues of sediment ingress through overland pathways. The wet weather walkover surveys were undertaken in December 2015. The walkover survey findings are graded according to their severity and risk to sediment ingress into a watercourse. Low Risk

Where land management practices are in close proximity to a watercourse but there is no visible sign of sediment transfer via an overland pathway into the watercourse itself. These sites will still need mitigation as they are still deemed a risk to sediment entering the watercourse during high rainfall events.


Medium Risk High Risk

Where land management, trackways and roads immediately adjacent to a watercourse are visibly causing sediment to enter the watercourse during high rainfall events. Where land management, trackways and roads immediately adjacent to a watercourse are visibly causing a high quantity of sediment and or organic material to enter the watercourse during all rainfall events.

Figure 1. – Combined risk of overland sediment pathways in the Hampshire Avon Catchment


The Three priority sub-catchments identified in the Upper Avon Catchment were Deane Water, Woodborough Stream and the West Avon Tributary. The results from the Upper Avon Wet Weather Walkover Surveys are detailed below.

Figure 2. – Priority catchments identified with APEM 2010 Data overlaid


Figure 3. – Deane Water priority catchments with APEM 2010 and flow pathways data overlaid

Figure 4. – Woodborough Stream priority catchments with APEM 2010 and flow pathways data overlaid

Figure 5. – Western Avon priority catchments with APEM 2010 and flow pathways data overlaid


River Name: Date Type of Input

Deane Water Site Number 1 06/12/2015 NGR SU1830261857 Silt, Heavy metals, Priority Medium Gravel Description Road Edge Material and from sediment transfer Land Use LHB: Formal Lawn RHB: Minor Road Vegetation LHB: Alder Trees, Ivy , Marginal plants RHB: Scrubby vegetation and Grass Comments: Although at the time of the survey no sediment run-off was observed; Road run-off from multiple channels cut into the road verge are flowing into the main channel. The verge is heavily eroded by road traffic. During high rainfall events water collects on the Roads and ponds. The cuttings allow the water to flow back into the main channel but will take all the sediments on the road with it. This area (being the bottom of the valley) also collects all the water from overland flow down 3 surrounding minor roads. Any sediment on the road during high rainfall events is washed down hill and enters the main channel at this point. Mitigation: Bespoke mitigation will need to be agreed and designed in consultation with Wiltshire Council (Highways) to widen the road or install curbing. Delivery Mechanism: Wiltshire Council (Highways) scheme


River Name: Date Type of Input Description Land Use Vegetation

Deane Water Site Number 2 06/12/2015 NGR SU1847761810 Silt Priority Low Cut up field and access track from vehicle movements LHB: Woodland, Natural grassland RHB: Woodland, Arable field LHB: Alder Trees, marginal plants, RHB: Alder Trees, marginal plants, Scrub Scrub, winter crop? Comments: The bottom corner of an arable field has been severely cut up by a turning farm vehicle. The trackway down to the river has also been rutted by machinery creating a pathway for any overland flow from the field down to the watercourse. This churning of sediment is quite severe and could cause a significant overland pathway. This site was flagged as an issue in the APEM 2010 survey (site 127) and it appears from visual evidence that a bridge across the river has been installed and a new trackway has been created on the RHB. Mitigation: Place the corner of the field into a lay aside scheme as return to natural grassland to prevent further turning and rutting. Look at other cropping options. Put a stone access into field to reduce run-off and/or install cross drains to intercept pathway and allow run-off to soak into the adjacent land. Delivery mechanism: Catchment Sensitive Farming (CSF) farm advice visit. Potential for Environmental Stewardship (ES) or new Countryside Stewardship (CS) Options. Also potential for Water Framework Directive (WFD) grant to upgrade the track.


River Name: Deane Water Site Number 3 Date 06/12/2015 NGR SU1873461839 Type of Input Sediment Priority Low Description Potential for Field run-off Land Use RHB: Arable Field Vegetation RHB: Winter Crop? Comments: Small Buffer strip on margin of field. Any overland flow pathways through the bare/exposed field will take sediment through the woodland into the stream. No pathways observed but in High rainfall events possibility for this to happen. Mitigation: Create a wider field buffer to slow the flows reaching the woodland strip, this will encourage sediment to be dropped on the grass buffer. Delivery mechanism: CSF farm advice visit. Use of ES or CS options.


River Name: Date Type of Input

Deane Water Site Number 4 06/12/2015 NGR SU1890161764 Sediment, Farm Yard Priority Medium Run-off Description Sediment and farm yard run-off into main channel via private access road Land Use LHB: Grazing Field RHB: formal Lawn, Farm Yard Vegetation LHB: Marginal vegetation, Woodland RHB: Grass, Marginal Plants Comments: Sediment from eroded road verges (due to farm machinery) and any sediment/organic matter from the farm yard runs downhill and collects at the lowest point of the road. A Channel has been cut into the bank to allow the water to drain off and is heavily incised due to the amount of water that has been going into the channel. At the time of the survey the pond that the drain had been cut into was very cloudy with sediment. This site was flagged as an issue in the APEM 2010 survey (site 121) but it appears that this issue has not been addressed. Mitigation: Widen the road to stop erosion and install curbing. Ensure that run-off from farm is not allowed to flow down the road with organic material as content by installing separation of clean and dirty water on the farm. Delivery mechanism: Potential for CS water grant for infrastructure improvements. Wiltshire Council (Highways) scheme.


River Name: Deane Water Site Number 5 Date 06/12/2015 NGR SU1922861679 Type of Input Sediment, Priority Medium Description Bare exposed soil due to pheasant pen around river Land Use LHB: Pheasant Pen RHB: Pheasant Pen Vegetation LHB: Some small trees RHB: some small trees Comments: A pheasant Pen has been set up around a watercourse. The birds have removed all the marginal bankside vegetation leaving bare soil that in high flow events will be mobilised and flow downstream Mitigation: Move Pheasants pen away from the watercourse and re-instate the bankside fencing to give a marginal buffer zone along the river corridor. Delivery mechanism: CSF farm advice visit. Potential for new CS options for riparian management.


River Name: Date Type of Input Description Land Use Vegetation

Deane Water Site Number 6 06/12/2015 NGR SU1903761931 Sediment Priority High Road verge and field run-off LHB: Woodland, grazed field RHB: Grazed and Arable field LHB: Hazel and alder trees, limited RHB: hazel and alder trees, limited marginal vegetation marginal vegetation Comments: sediment from an arable field and erosion from road verges is running off the highway into a formal drain on either side of the highway which exits under the road bridge. Supplementary channels have been cut into the verge to take excess run-off during heavy rainfall events when the drains are blocked/cannot cope with water influx. This site was flagged as an issue in the APEM 2010 survey (site 120) and it appears that this issue has not been addressed. Mitigation: Upgrade the field access to gravel and install cross drain at bottom of track with soakaway to side of track. Widen the road/add curbs and change road drainage to allow for SUDS to be installed before run-off enters the watercourse. Delivery mechanism: CSF farm advice visit with respect to management of access to arable field. Potential for ES or new CS options and/or WFD grant for track works. Highways scheme may be able to protect the road verge, unblock the drains and investigate the need for SUDs.


River Name: Date Type of Input Description

Woodborough Stream Site Number 7 06/12/2015 NGR SU1386560576 Sediment Priority Medium Degraded trackway with sediment entering the main channel during high rainfall events Land Use LHB: Woodland, grazed field RHB: Woodland, grazed field Vegetation LHB: Grass, Small trees, limited RHB: Grass, Small trees, limited marginal vegetation marginal vegetation Comments: A degraded trackway acts as a conduit for sediment laden water during high rainfall events running downhill from the field to the south and the roadway to the North. This site was flagged as an issue in the APEM 2010 survey (site 129) and it appears that the issue has not been resolved. Mitigation: Upgrade the track and install cross drains so the run-off is dissipated into adjacent land before it reaches the river. Delivery mechanism: WFD grant and/or Highways Scheme.


River Name: Date Type of Input Description Land Use Vegetation

Woodborough Stream Site Number 8 06/12/2015 NGR SU1424560446 Sediment Priority High Road verge erosion running downhill via a highway into the watercourse LHB: Woodland, grazed field RHB: Woodland, grazed field LHB: Grass, Small trees, limited RHB: Grass, Small trees, limited marginal vegetation marginal vegetation Comments: sediment from erosion of road verges is running off the highway into the watercourse. Supplementary channels have been cut into the verge to take excess run-off during heavy rainfall events when the drains. This site was flagged as an issue in the APEM 2010 survey (site 133) but it appears not to have been resolved. Mitigation: Install protective curbing and passing bays and improve the road drainage. Delivery mechanism: Wiltshire Council Highways scheme.


River Name: Date Type of Input Description Land Use Vegetation

Woodborough Stream Site Number 10 06/12/2015 NGR SU1494060096 Sediment Priority Low Bare Soil on cut maize field LHB: Woodland, bare arable field RHB: Woodland, grazed field LHB: Woodland, Grass field edge, Cut RHB: Woodland, Grass Maise crop Comments: Although at the time of the survey no sediment run-off was observed, A bare maize field on the LHB is contributing sediment to a feeder spring for the main channel. The Buffer strip that is place on the field is very narrow and immediately transitions into a steep slope. Any High rainfall events will cause water to pick up sediment and transfer into the feeder ditch. This site was flagged as an issue in the APEM 2010 survey (site 137) but it appears to still be an issue. Mitigation: Increase the width of the buffer strip and consider changing crop/cover crops over winter. Dress the field access with stone. Delivery mechanism: CSF farm advice visit. Potential for ES or CS options and capital grants.


River Name: Woodborough Stream Site Number 11 Date 06/12/2015 NGR SU1504059306 Type of Input Not Known Priority Medium Description Milky/high loading of fine sediments in the watercourse Land Use LHB: Woodland, Formal Lawn RHB: Woodland Vegetation LHB: Established trees/ none RHB: established trees/None Comments: High fine sediment loading was noticed entering upstream of the road bridge. Source is unknown as private land. Surveyor was able to access the river at SU1511759633 where the presence of fine sediment was not noticed. A site upstream was flagged as an issue in the APEM 2010 survey (site 141) with a farm access track noted for being a pathway for sediment into the channel. Mitigation: Further investigation is needed. Delivery mechanism: CSF Farm advice visit.


The results from the Were/Swan Wet Weather Walkover Surveys are detailed below.

Figure 1. – Priority catchments identified with APEM 2010 Data overlaid


Figure2. – Swan/Were Priority catchment identified with APEM 2010 Data overlaid


River Name: Date Type of Input Description

Swan/Were Site Number 1 23/12/2015 NGR ST8673747106 Silt, Organic Material Priority Medium Massive soil pile next to watercourse with access track to and from creating sediment pathway Land Use LHB: Arable field RHB: Minor Road Vegetation LHB: Overwintering crop RHB: Scrubby vegetation and Grass Comments: Although at the time of the survey no sediment run-off was observed, a large sediment pile is in close proximity to the watercourse. Any high rainfall events cause ponding on the bridge over the watercourse which is the main access to the field where the soil is stored. The ponded area had a high sediment loading and could only drain into the watercourse, taking the sediment with it. The Road verge is also heavily poached by farm vehicles and a low density of traffic causing additional sediment in the ponded are during high rainfall events. This site was flagged as an issue in the APEM 2010 survey (site 45) and it appears that nothing has changed. Mitigation: Move soil pile so that any run-off from the field/road does not pond near the watercourse. Create a wider buffer strip next to the watercourse. Delivery mechanism: CSF farm advice visit.


River Name: Swan/Were Site Number 2 Date 23/12/2015 NGR ST8679746911 Type of Input Silt, Organic Material Priority Medium Description Run-off from road and arable field during high rainfall events Land Use LHB: Arable field RHB: Minor Road Vegetation LHB: Overwintering crop RHB: Scrubby vegetation and Grass Comments: Although at the time of the survey no sediment run-off was observed, a channel has visibly been cut in to the field to allow any ponded water in the arable field to escape into the drainage network which leads into the top end of the Were/Swan. There has also been a drainage pipe put in to remove any water that ponds on the minor road. The Minor road is very heavily eroded along both banks by farm and normal traffic which means any heavy rainfall events will transfer sediment into the main watercourse. Mitigation: Create a buffer strip adjacent to the watercourse to prevent loss of soil. Create a new pond and divert field drain into this or replace the drain with a grass swale. Wiltshire Highways will need to look at options for dealing with the water ponding on the road, there is potential for silt trap but it would need some land take. Delivery mechanism: CSF farm advice visit. Potential ES or CS options. Wiltshire Council Highways scheme.


River Name: Date Type of Input

Swan/Were Site Number 3a 23/12/2015 NGR ST8695745985 Silt, heavy metals, Priority High pollutants, Fine Sand Description Drainage pipe run-off from industrial estate Land Use LHB: Public Footpath, Lake RHB: Scrub, Woodland Vegetation LHB: Grass RHB: Scrubby vegetation, small trees Comments: At the exit of the drainage pipe from the industrial unit a high level of sediment is visible in channel and also upstream in the pipe. This material consists of sediment and fine gravels. There is also a lot of industrial waste in the form of gloves and plastic packaging within the material and caught in the grill at the end of the drainage pipe. Mitigation: Place the drainage channel into a SUDS to filter out any sediments before they reach the main watercourse. Tackle the issue of oil and other contaminants with immediate effect. Delivery mechanism: Contact the management company for the industrial estate and talk to them about tackling the problem/ Speak to the individual companies and get them to change practices and deal with the issue at source. Possible WFD funding.


River Name: Date Type of Input

Swan/Were Site Number 3b 23/12/2015 NGR ST8695745985 Silt, heavy metals, Priority High pollutants, Fine Sand Description Drainage pipe run-off from industrial estate Land Use LHB: Scrub, Woodland RHB: Scrub, Woodland Vegetation LHB: Scrubby vegetation, small trees RHB: Scrubby vegetation, small trees Comments: At the exit of the drainage pipe from the industrial unit a high level of sediment is visible in channel. This material consists of sediment and fine gravels. There is also a film of oily pollutants over the marginal vegetation at the exit of the pipe. Mitigation: Place the drainage channel into a SUDS to filter out any sediments before they reach the main watercourse. Tackle the issue of oil and other contaminants with immediate effect. Delivery mechanism: Contact the management company for the industrial estate and talk to them about tackling the problem/ Speak to the individual companies and get them to change practices and deal with the issue


River Name: Swan/Were Site Number 4 Date 23/12/2015 NGR ST8687446277 Type of Input Sediment Priority Low Description Drainage channel from derelict land Land Use LHB: Scrub, Woodland RHB: Scrub, Woodland Vegetation LHB: Scrubby vegetation, small trees RHB: Scrubby vegetation, small trees Comments: The edge of some derelict land has had a bund built on the bottom of the slope closest to the watercourse. Into the bund 2 channels have been dug to take away water that would have ponded on the land side of the bund during wet weather events (visible during the walkover). The channels through the bund have been partially infilled with loose building quality soil which does not have any established vegetation and will wash down through drainage channels straight into the watercourse during wet weather events. There has also been a number of soil piles dumped immediately next to the watercourse. During high rainfall events the loose un-vegetated sediment will transfer straight into the watercourse. Mitigation: Needs investigation as to whether this is consented work (under planning, FDC or Ordinary Water Course consent) and if so follow up with consenting authority as not effective mitigation. If it is permanent could place the 2 drainage channel into a SUDS to filter out any sediments before they reach the main watercourse. Delivery mechanism: EA to follow up if it is breach of planning or FDC.


River Name: Date

Swan/Were ? 23/12/2015

Site Number NGR

5 ST8512444949 To ST8578745162 Medium

Type of Input Sediment Priority Description Drainage channel from derelict land Land Use LHB: Scrub, Woodland RHB: Scrub, Woodland Vegetation LHB: Scrubby vegetation, small trees RHB: Scrubby vegetation, small trees Comments: Small Buffer strip on field margin directly next to the channel. In a number of places the margin is heavily compacted and has puddles of standing water. This continues through both fields all the way up to the A36. Mitigation Action: Increase the buffer strip along the edge of the field margin along the course of this channel. Delivery mechanism: CSF farm advice visit. Potential ES or CS options.


River Name: Swan/Were ? Site Number 6 Date 23/12/2015 NGR ST8595745137 Type of Input Sediment Priority Medium Description Drainage SUDS pond filled with sediment leaching into the main river Land Use LHB: Scrub, Housing RHB: Scrub, Housing Vegetation LHB: Scrubby vegetation RHB: Scrubby vegetation Comments: Drainage SUDS pond from housing estate is full of sediment and silt from road run-off and other unidentified sources. There is already a substantial growth of watercress on the top of the sediment. During high flows, any sediment laden water that enters the pond flows over the surface of the pond and into the outfall with little or none deposited in the pond. The entrance pipe has also cracked or split underground and water is entering the lake around the pipe increasing the risk of sediments entering the pond. Anecdotal evidence from local residents confirm that large quantities of ‘brown water’ are often seen exiting the pond into the main watercourse. Mitigation: Improve the SUDS at this site to filter out more Sediment. Trace the under street drainage network to try and find the source of the majority of sediment and material that enters the SUDS pond. Delivery mechanism: Establish who is responsible for maintenance of SUDS, either Wiltshire Highways or the Housing association.


River Name: Date Type of Input Description Land Use

Swan/Were Site Number 7 23/12/2015 NGR ST8801444284 Sediment Priority Medium Road run-off LHB: Nature Reserve, Managed RHB: Nature Reserve, Managed woodland woodland, Car Park Vegetation LHB: Scrubby vegetation, small trees RHB: Scrubby vegetation, small trees Comments: A B-road at the bottom of the valley has no roadside verge to the main watercourse and runoff from the eroded road is drained off directly into the river channel causing sedimentation of the channel. There are also road drains that exit immediately into the watercourse that have caused visible sedimentation in the main channel. Mitigation: Advice Required From Wiltshire Council for bespoke mitigation, potential for road widening and/or curbing. Delivery Mechanism: Wiltshire Council Highways Scheme.


The results from the Upper Wylye Wet Weather Walkover Surveys are detailed below.


Figure 1. – Priority catchments identified with APEM 2010 Data overlaid

Figure 2. – Upper Wylye Priority catchment identified with APEM 2010 Data overlaid


Figure 3. – Upper Wylye Priority catchment identified with APEM 2010 Data overlaid


River Name: Date Type of Input Description Land Use

Wylye Site Number 8 23/12/2015 NGR ST8793643701 Sediment Priority Low Potential for road run-off, large sediment ingress LHB: Private Garden, Fishing Lakes RHB: Historic Watermeadows, Woodland Vegetation LHB: Formal Lawn, Small Trees RHB: scrubby grassland, small trees Comments: A private minor road leading to the bottom of the valley has been eroded by farm traffic and in high rainfall events has the potential to deliver a high quantity of sediment to the main watercourse. The sediment laden water is currently held back by a rise in gradient but when visiting the site it was deemed that any further water would flow over the gradient and down the rest of the Track/Public Footpath. Mitigation: Create drainage channels into adjacent land. Delivery mechanism: WFD funding or CSF visit.


River Name: Date Type of Input Description Land Use Vegetation

Wylye Site Number 9a 23/12/2015 NGR ST8724343143 Sediment Priority Medium Road run-off LHB: Formal Lawn, Pasture RHB: Woodland, Formal Lawn LHB: Formal Lawn, Pasture Grass RHB: Formal lawn, scrubby grassland, Small Trees small trees Comments: Sediment laden water from eroded verges uphill of the location collects on a highway during high rainfall events. Cuttings in the verge transfer the water into a heavily silted drainage ditch which exits into the main watercourse. A complex drainage structure exists that also takes some of the water under the road and into a drainage channel that flows upstream towards the sluices at the Mill. Mitigation: Bespoke advice required from Wiltshire Council as to how this can be tackled as a Highways issue to reduce erosion of banks at uphill location, may require road widening, passing places and/or curbing. Delivery Mechanism: Wiltshire Council Highways Scheme.


Main Watercourse


River Name: Date Type of Input Description Land Use Vegetation

Wylye Site Number 9b 23/12/2015 NGR ST8724343143 Sediment Priority Medium Road run-off LHB: woodland RHB: Horse Field LHB: Small Trees, Scrubby vegetation RHB: Pasture grass, Scrubby vegetation Comments: Sediment laden water from eroded verges uphill of the location enters a road drain and directly passes overland into the main watercourse upstream of the road bridge. Mitigation: Bespoke advice required from Wiltshire Council as to how this can be tackled as a Highways issue to reduce erosion of banks at uphill location, may require road widening, passing places and/or curbing. Delivery Mechanism: Wiltshire Council Highways Scheme.


Main Watercourse


River Name: Date Type of Input Description Land Use Vegetation

Wylye Site Number 10 23/12/2015 NGR ST8604342392 Sediment Priority Medium Road run-off LHB: woodland RHB: Horse Field LHB: Small Trees, Scrubby vegetation RHB: Pasture grass, Scrubby vegetation Comments: Sediment laden water from eroded verges uphill of the location enters the main channel through cuttings and drainage channels directly into the main watercourse. Mitigation: Bespoke advice required from Wiltshire Council as to how this can be tackled as a Highways issue to reduce erosion of banks at uphill location, may require road widening, passing places and/or curbing. Delivery Mechanism: Wiltshire Council Highways Scheme.


River Name: Wylye Site Number 12 Date 23/12/2015 NGR ST8683840757 Type of Input Sediment Priority High Description Field poaching at a drinking bay Land Use LHB: Formal Gardens RHB: Pasture Field Vegetation LHB: Scrubby trees, Formal Lawn RHB: Pasture grass Comments: A heavily poached bank exists right along the RHB of this field due to cattle access for drinking water. The section photographed has greened up as it hasn’t been used recently but heavy sedimentation can be seen at and downstream of the location. This and the rest of the field needs to be managed to prevent sediment entering directly into the watercourse. This site was flagged as an issue in the APEM 2010 survey (site 51) and it appears to have still not been addressed. Mitigation: Marginal fencing with a buffer strip with potential to install a pasture pump as water supply and or designated hard standing formal cattle drinks. The field margin could be fenced off at vulnerable times of year with electric fencing or fenced with a wide margin to allow cattle in at times when the ground is firmer so as to graze off the vegetation whilst not eroding the bank. Delivery mechanism: CSF farm advice visit. Potential ES or CS options.


River Name: Date Type of Input Description Land Use

Wylye Site Number 13 23/12/2015 NGR ST8259537227 Sediment Priority Low Heavily eroded arable field from farm traffic LHB: Woodland plantation, Arable RHB: Pasture, woodland plantation Field Vegetation LHB: Overwintering crops, Poplar, RHB: Poplar, Pasture grass Scrubby vegetation Comments: Heavily eroded field from farm traffic is collecting water at the bottom of a steep sloped arable field. The water collected is high in sediment and cuttings have been placed in the field margins into the woodland to allow run-off when the field is saturated and water saturated land is present. Mitigation: Increase field margins and create swales or grassy areas to absorb the water. Look at crop management to prevent requirement for driving over very wet ground and stopping compaction of soil. Delivery mechanism: CSF farm advice visit. Potential ES or CS options.


Main Watercourse


River Name: Date Type of Input Description Land Use Vegetation

Wylye Site Number 14 23/12/2015 NGR ST8250037212 Sediment Priority Medium Moderately poached field gate LHB: Pasture Land RHB: Arable field, Scrubby grassland LHB: permanent Pasture RHB: Over Wintering Arable Crops, Scrubby Grass Comments: Field access gate which crosses the main watercourse is poached by cattle/sheep. Water is ponding on clearly compacted soils and is running off directly into the main watercourse. Mitigation: Install hard surface for field gate to prevent further erosion and sediment ingress. Delivery mechanism: CSF farm advice visit. Potential ES or CS options.


River Name: Date Type of Input Description Land Use Vegetation

Wylye Site Number 15 23/12/2015 NGR ST8118536742 Sediment Priority Medium Sediment laden water exiting drainage pipe into sediment laden ditch LHB: livestock field RHB: Hedgerow and road LHB: Pasture grass RHB: Hedgerow plants and roadside verge grass Comments: The main priority of this site is the drainage pipes which enter the ditch nearest the gate. The surveyor noted that one pipe ran with clean water and the other ran very turbid and dirty. There is a set of cattle barns upstream of the ditch and it is imagined that the water is coming from here. The ditch that the water enters into is heavily silted with an iridescent film on the water flowing over the surface of the ditch. There is also a field gate which is particularly muddy due to farm traffic. The gateway also acts as a gully for all the sediment and farm yard effluent that flows downhill on the private access road. (See Site 16 for more details). Mitigation: Identify source of turbid water in ditch if coming from the farm then recommend clean and dirty water separation units and give advice on how to maintain these units. If soil is heavily compacted create wider buffer strips to catch sediment from the water before it goes into the ditches by moving the fencing back from the ditch. Improve gate access with hard standing to reduce erosion. Delivery mechanism: CSF farm advice visit. Potential ES or CS options.


Main Watercourse


River Name: Date Type of Input Description Land Use Vegetation

Wylye Site Number 16 23/12/2015 NGR ST8108936838 Sediment, farm effluent Priority Medium sediment and farm effluent running downhill on a private road to Site 15 LHB: Farmyard, pasture RHB: Pasture, Arable field, Housing LHB: Grassed Roadside Verge, RHB: Grassed Road Verge, Hedgerow, Hedgerow vegetation pasture grass Comments: Heavy rainfall events leads to water running down the edges of the road and picking up farm pollution from gateways and from the entrance to the farm yard. Water then runs through the gateway at Site 15 and into the drainage ditch. Mitigation: Create cuttings in road verge to take water before it flows into the field gate. Relocate manure heap away from sediment pathways and put in hard standing at gateway. Delivery mechanism: CSF farm advice visit. Potential ES or CS options.


River Name: Date Type of Input Description Land Use Vegetation

Wylye Site Number 17 23/12/2015 NGR ST8123036660 Sediment, road run-off Priority High Eroded verge with cuttings supplying sediment into the main river channel LHB: Pasture grassland RHB: Arable field LHB: Pasture grass, Hedgerow, RHB: Arable crops, grassed Road grassed Road Verge Verge Comments: During high flows water is flowing overland down the tarmac road along the road verge picking up sediment from eroded areas. A cut through has been created in the verge to take the water off the road and prevent ponding during high rainfall events to the detriment of the watercourse. The watercourse downstream of the hedgerow is heavily silted and turbid during rainfall events. Mitigation: Create cuttings in the road verge further up the road to allow water to drain off before the main watercourse cutting. Delivery mechanism: Wiltshire Council Highways scheme


Main Watercourse


River Name: Date Type of Input Description

Wylye Site Number 18 23/12/2015 NGR ST8060036345 Sediment, farm effluent Priority High Raw farm effluent is passing from the farmyard into a drainage ditch that leads to the main watercourse Land Use LHB: Arable/pasture farmland RHB: Arable/pasture Farmland Vegetation LHB: Arable crops/ pasture grass RHB: Arable crops/ pasture grass Comments: Raw Effluent is coming out of the farmyard across the main track and into a drainage ditch that flows into the main watercourse. Efforts have been made to place boards across the ditch to hold back and prevent the flow of effluent but these are now full to the top and there has been no effort to clear them out. The main track also leads uphill to a muddy horse field at the top and water is flowing downhill along the track into the same drainage ditch taking sediment with it. A photo of the farm yard exit is not present as the farmer was present and the surveyor did not want to cause problems during the visit. Mitigation: Create cuttings to drain the water off ditch, look at creating a new pond to take flow and sediment. Install clean and dirty water separation units in the farmyard to deal with effluent from farm and ensure that they are given advice on how to maintain units. Delivery mechanism: CSF farm advice visit and CS water grant.


Main Watercourse

Main Watercourse


River Name: Date Type of Input Description

Wylye Site Number 19 23/12/2015 NGR ST8448037170 Sediment, road run-off Priority Low Sediment from eroded verges and field access gates running downhill into road drains Land Use LHB: Farm yard, housing and arable RHB: Arable field, housing fields Vegetation LHB: Road Verge, Hedging and arable RHB: Road Verge, Hedging and crops arable crops Comments: eroded road verges and heavily damaged access gateways are transferring sediment downhill along the main road into a road drain which exits into the main watercourse Mitigation: Bespoke advice required from Wiltshire Council as to how this can be tackled as a Highways issue, there is potential for drains to direct flow onto surrounding land and improve gateways with hard standing. Delivery mechanism: Wiltshire Council Highways Scheme. CSF farm advice visit.


Main Watercourse


River Name: Date Type of Input Description

Wylye Site Number 20 23/12/2015 NGR ST8441537057 Sediment, road run-off Priority Medium Sediment running off through cuttings into side channel which feeds the main watercourse Land Use LHB: Formal gardens RHB: Formal gardens Vegetation LHB: grassed road verge, garden RHB: grassed road verge, garden Comments: during high rainfall events sediment from eroded road verges runs downhill along the main road and is taken off into a side channel that feeds the main watercourse. Mitigation: Bespoke advice required from Wiltshire Council as to how this can be tackled as a Highways issue, using passing places, curbing and drainage on the other side of the road, camber away from watercourse. Delivery mechanism: Wiltshire Council Highways scheme.


River Name: Wylye Site Number 21 Date 23/12/2015 NGR ST8443337101 Type of Input Sediment Priority Medium Description Sediment from a pipe exiting into the watercourse Land Use LHB: RHB: Vegetation LHB: RHB: Comments: A Pipe exiting from private gardens has a visible amount of sediment entering directly into the watercourse. There was no visible explanation for why the pipe was there. Mitigation: Further investigation is needed into the source of the pipe and its purpose. Delivery Mechanism: Environment Agency need to follow this up as a potential pollution source.


Main Watercourse

River Name: Date Type of Input Description

Wylye Site Number 22 23/12/2015 NGR ST8463237165 Sediment, road run-off Priority Medium Sediment ingress into the river from road run-off by land drain and other flow pathways Land Use LHB: Private Gardens RHB: Private Gardens Vegetation LHB: Formal Lawn, Hedgerows RHB: Formal Lawn, Hedgerows Comments: Sediment from road verge erosion and other sources during high rainfall events is transferring overland into road drains, which exits straight into the channel, and via an informal cutting through a hedgerow and private garden. The informal cutting has been created to stop water ponding on the main road.


Mitigation: Bespoke advice required from Wiltshire Council as to how this can be tackled as a Highways issue, with the potential for directing flow onto adjacent land. Delivery mechanism: Wiltshire Council Highways Scheme.


Road Drain


River Name: Date Type of Input Description Land Use Vegetation

Wylye Site Number 23a 23/12/2015 NGR ST8512237247 Sediment Priority Medium Sediment from track and field run-off entering the watercourse LHB: Rough grassland, formal garden RHB: Horse pasture LHB: scrubby grass, some trees, RHB: Pasture grass, some trees, hedgerows hedgerows Comments: South of Ford crossing point (byway) on the river Wylye with heavily poached verge banks and track. Access track from horse field is adding to sediment entering the main watercourse during high rainfall events. Mitigation: Improve access to field gate by putting in hard standing, thus reducing erosion. The ford will need to be investigated by Wiltshire Highways, potential to create drainage channels to divert water onto adjacent land before it reaches the ford and re-surface byway to reduce erosion. Delivery mechanism: CSF farm advice visit. Wiltshire Council Highways scheme.


River Name: Date Type of Input Description Land Use Vegetation

Wylye Site Number 23b 23/12/2015 NGR ST8512337294 Sediment Priority Medium Sediment from track and field run-off entering the watercourse LHB: Rough grassland, formal garden RHB: Horse pasture LHB: scrubby grass, some trees, RHB: Pasture grass, some trees, hedgerows hedgerows Comments: North of Ford crossing point (byway) on the river Wylye with heavily eroded verge banks and track. Access track from arable field is causing sediment to enter the main watercourse during high rainfall events. Mitigation: Improve access to field gate by putting in hard standing, thus reducing erosion. The ford will need to be investigated by Wiltshire Highways, potential to create drainage channels to divert water onto adjacent land before it reaches the ford and re-surface byway to reduce erosion. Delivery mechanism: CSF farm advice visit. Wiltshire Council Highways scheme.


Main Watercourse

Main Watercourse


Mitigation strategies can be found on the following websites:

Swales and retention ponds: http://www.susdrain.org/delivering-suds/using-suds/sudscomponents/retention_and_detention/retention_ponds.html Information sheets from the Rivers Trust (dirty water separation, farm access, hard standing, buffer zones, stream crossings): http://www.theriverstrust.org/pinpoint/info_sheets.html

Profile for HACP

Avon sediment pathways 2016 wcsrt report  

Avon sediment pathways 2016 wcsrt report  

Profile for hacp0
Advertisement