The Lye Fen – Another Death Blow

Oxford City Council Delivers Another Death Blow to The Lye Fen

What is the Issue?

Oxford City Council is seeking planning permission in effect to construct an underground dam of concrete foundations across the head of the Lye valley feeding the Lye Fen SSSI (North) and the Lye Local Nature Reserve (LNR) at the point where it crosses Girdlestone Road at the Town Furze estate:

20/00463/FUL | Erection of 2 x 3-bed semi-detached dwellinghouses (Use Class C3). Provision of bin and cycle storage and alterations to landscaping. | 2 Dynham Place Oxford Oxfordshire OX3 7NL

See also: Lye Valley  for the disasterous 10 house development at Warren Crescent Meadow and Ellie The Elk On The Lye

Appeal

Please Join Friends Of Lye Valley (FOLV) to help save this precious place:

Web:    http://www.friendsoflyevalley.org.uk
email: friendsoflyevalley@yahoo.co.uk

Updates

Since below was written further research and fieldwork has confirmed that “Girdlestone Gully” is actually  part of the main valley so is referred to as the “Upper Lye.”  See  The Upper Lye Valley – Headington’s Secret Garden – many other new details.

Summary

The development will do severe additional hydrological damage to the Lye Fen (SSSI), an already weakened and vulnerable ecosystem due the effects urbanisation and climate change.

The approval of the 10 house Warren Crescent (13/01555/CT3) on Warren Meadow robbed local children of the only open green space who can only play on the road (except toddlers) – to understand the great damage this development will do alone, see below for the overall context:

The Hymn Of The Lye

 Warren Crescent and Dynham Place (DP) Oxford City Council developments will form adjacent concrete underground dams by compression and blockage, choking off the last source of groundwater for the last tiny remnant of the Lye Fen, already reduced to a fraction of its natural size.

NO investigation for either development has been performed to determine the overall Lye hydrology, in particular, the effects of the overall critical catchment flows feeding the Fen.

 The ground investigation reports address only the effect of the Lye geology and hydrology on the development, and rainwater ON the site, not groundwater flows THROUGH the development sites to the Lye Fen.

 The Warren Crescent development has paused due to the COVID-19 lockdown, so far the damage is minor and reversable and can still be stopped before it is too late.

 The Council appears to be happy to risk destroying this rare ice-age relict fen without any understanding of the hydrology, critical to its survival.

 THERE IS NO BACKOUT, CHANGES ONCE MADE WILL BE IRREVERSIBLE

 Changes to the Lye have been, and can be sudden, as per the 1979 event described below, and catastrophic as any margin of safety is long gone in this deeply damaged ecosystem.

What Can I Do?

The official consultation is now over but a determination has not yet been made, approximately 50 objections were made.

You can email planning@oxford.gov.uk, (click) citing above application and your local Councillor.

This can not be called in due to Oxford’s  increasingly undemocratic constitution that now only allows decisions to go to Councillors at the Area Committee if they are called in by six or more with 21 days of publication of the application – this is practically impossible, as the Council is often late placing yellow notices up, time to study is required and Councillors need to be contacted, appraised of the sometimes very technical nature of the objections and  persuaded to call in.

What are The Main Points?

The proposed Dynham Place development is on the north side of Girdlestone Road, close to the Warren Crescent development.

WC_DP_contour

The Development Location with Contour Overlay

WC_DP_from_north_now

Lye Valley From North – Now

WC_DP_from_north_1945_ok

Lye Valley From North – 1945

WC_DP_from_east_1945

Lye Valley From East 1945 – Note Steep Slopes

The points to note above are:

  • The basic form of the Upper Lye (formerly referred to as Girdlestone gully below) and Slade Gullies is shown above with a red line at the 93m contour on the first image. [Plan1954]
  • The Dynham Place development straddles the Upper Lye valley north of Girdlestone Road shown in yellow
  • The Upper Lye Valley (Girdlestone Gully) is almost certainly the source of the Lye due both to its alignment and depth (See 1945 map above)
  • The Upper Lye Valley is now partially filled with Made Ground in common with the Warren Crescent development from the 1958 (approx.) Town Furze Estate development (compare images)
  • The surface slopes gently down from the green 97m contour to the west to the gully and the main Lye valley with land sloping down in from Headington to the north and Shotover to the east. (see first map)
  • Wells (grouped) following the line of the gully base in the allotments immediately below the DP development site have water, indicating the presence of flows immediately below from the gully
  • In common with the Warren Crescent Development, this land was not previously developed as it was identified as not suitable in 1958 (approx)
  • The 1945 maps show Peat Moors slope as artificial and much steeper then
  • The Warren Crescent Development land is flatter and not yet build up with made ground as per Peat Moors above
  • The Upper Lye (Girdlestone Gully) is much deeper than today as not yet filled in with Made Ground
  • It is possible the The Slade Gully (the footpath from The Slade and entrance point to the Lye) may have received similar flows due to the high elevations of Shotover to the immediate east
  • A Local Nature Reserve (not shown) extends over almost all of the Lye valley.

The presence of peat in the ground indicates this was former fen (as was the now covered valley slope at the Warren Crescent development)

[1]The Google mapping between now and the 1945 map is not exact, possibly the development is slightly further to the south than shown.

[2] The red line shown in the last three maps is not precisely the same as the first map, drawn around where the valley is visible.  Digitised maps must be treated with some caution.

What Does It It Look Like?

DynhamPlace2

The Development Site – Girdlestone Road Looking towards The Slade

The proposed DP development looking from Girdlestone Road is shown below:

WC_DP_Foundations

Dynham Place Looking From Girdlestone Road

The above diagram shows the DP development from Girdlestone Road with a lower split level at the rear on top of the natural buried surface of the Girdlestone Gully (brown) with Made Ground above. [Map1954, GIS-2,p13,14]

The proposed 10m deep foundations comprised of Contiguous Bored Piles/Secant Piles will form in effect a concrete dam across and below the gully, necessary due to the Made Ground below. [GIS-1,p47]

What Damage Will It Do?

The development will:

  • Crush and rupture the aquifers below it and any underground watercourse that may be below
  • Permit groundwater from the surrounding high ground or in the aquifers to leak directly down where it will be wasted (The Lye is 85m to the south of this position and below the fen), rather than continue to be enriched and to flow to the seepage lines or to the Lye Brook directly
  • Prevent the gully from providing surface water in times of drought

The Hydrology of the Lye – An Overview

The diagram [Pre-EIA,p11,Fig 2] below illustrates the overall placement of the Lye Brook and fen surrounded by Beckley Limestone (mineral content) (Dark Brown) and Beckley Sands (Yellow), both producing perched water tables.  [Pre-EIA,p11].  The Lye SSSI is shown a green boundary below.

WC_DP_Flows_Lye

Lye Valley Geological Overview

Multiple mixed strata are present in the Lye Brook valley area.  To the east Shotover Hill rises surrounded by impermeable Ampthill Clay. (Blue Hatched, top right)

Groundwater – The Lifeblood of the Lye

The fen (86 AOD) is primarily nurtured by alkaline rich springs and seepages emerging at the 89 AOD level above it, created by rainfall infiltrating into the ground and flowing over and through calcium and other mineral rich strata, forming a series of perched water tables above the fen where it can supply it:

Fenland depends on a constant flow of ‘base rich’ groundwaters with high concentrations of 50 to 300 mg/l calcium balanced by hydrogen carbonate (or bicarbonate), dissolved carbon dioxide and sulphate (Hájek, 2002). [Pre-EIA, p19]

The hydrology is very delicate, dictated by multiple thin layers of strata with very specific features of density, permeably and chemical composition and hydrostatic conductivity which gently slope NE-SW  directing the flow. [Pre-EIA, p16, Fig 4]

In the immediate vicinity of the Lye Brook Valley, flows have been measured more southerly at Warren Crescent. [WSP LQA, PBA Final]

Natural Storm/Surface Water

Surface water landing as rain in the catchment the Lye flows as shallow groundwater down the surface contours, probably  following the groundwater strata only when reaching that level, therefore over short distances near the Lye the surface contours (which can be opposite to strata angles) will play an important role in determining the direction of water flow.

  1. Shallow groundwater will tend to follow the topology of the surface. [Pre-EIA, p9]

It is therefore probable that underground flows under the Upper Lye and Slade gully (see below) at the head of the stream are fed with water from the surrounding high ground, probably explaining their creation.

Hydrology – Pre-Human

A closer view of above shows the hydrology as it was prior to human alteration with the development sites (WC and DP, yellow) shown:

WC_DP_Flows_Close_pre

Lye Valley Hydrology – Pre-Human

Flow thicknesses shown correspond to relative flows.

  • Rain falls on thick vegetation (Dark Green) where it is retained by roots with some surface evaporation
  • Water infiltrates, descending to and along the NE-SW sloped strata underground via aquifers and (Light blue)
  • Arriving at the Lye valley it forms a strong spring and seepage line above the Lye and the fen, on both sides
  • Water falls gradually through the still extant fen to the Lye Brook, in the exact chemical composition required
  • Flows have minimal fluctuation during the year due to gradual recharging and discharge, allowing the fen to survive storm and drought conditions.
  • Very minimal surface water flows exist (blue)

Hydrology – Present Day

The current situation is illustrated below:

WC_DP_Flows_Close_now

Lye Valley Hydrology – Present Day

  • Most of the original Fen has disappeared due to lack of groundwater  and blocked flows
  • Rain falls on housing estates and roads (indicative Purple), consisting of impermeable surfaces such as roads, driveways and roofs and is directed into drains (Sewer Grey), leading to strong flows in storms
  • The “Evil Drain” discharges a mixture of rainwater, some sewage, and pollutants into the head of the Lye Brook just below the DP development

Made Ground or tipped embankments at the WC development site (created approx. 1958) and on the opposite side of the valley at Peat Moors have blocked the seepage lines , and have created ground instability.

The adverse consequences for the fen are:

  • The groundwater flows (light blue) are severely reduced as rainwater is redirected into the storm water drains, leading to weakened seepage and springlines, water is mostly lost to the fen as it flows below it via the Lye Brook
  • The stormwater does not acquire the alkaline composition required to nourish the fen but instead some sewage and industrial pollutants (Sewer Grey)
  • The Thames Water Surface Water/Storm Drain or the ‘evil’ drain, emerging just below the development site, has a much larger catchment that the natural one, stretching as far as Bury Knowle Park and Central Headington, bringing very substantially higher than natural flows
  • The flow is highly variable, with extremely high flows in storm conditions, no longer attenuated as it fell on now destroyed vegetation
  • High flows have and do cause severe incision in the Lye Brook stream bed, further depriving the fen of water as it is then left high and dry  (1m drop in 1979 alone) [Pre-EIA,p27]
  • In drought conditions the flow is absent
  • Much of the fen is now covered in Made Ground, or died from lack of groundwater, only a tiny remnant now remains

Victorian photographs show a much smaller and shallower Lye Brook than today indicating increased surface flows (See The Lye – Taunt In Colour )

As a result of the above the surviving fens in the Lye North SSSI are under severe threat, it is now dependent only on the reduced flows of the springlines immediately above them.

Hydrology – Post-Developments

The future following completion of the WC and Dynham Place developments is as per the current situation with the following additional negative features:

WC_DP_Flows_Close_post

Lye Valley Hydrology – Post-Development

  • Both developments are located on the flow lines to the Lye, north of the western fen which now dies (black squiggle)
  • The thin light blue groundwater flow to the two developments is now abstracted firstly by the Dynham Place development, leading to reduced hydrostatic pressure
  • Any remaining flow (shown red) is now blocked by compression by an underground wall of foundations at both developments, blocking the last source of groundwater for the western fen.

 The following shows the approximate catchment [Pre-EIA] corresponding to the Protection Zones advocated [Pre-EIA] and blocked flows of the Lye:

WC_DP_Catchment_1

Groundwater flows will be blocked RED by Oxford City Council Developments at WC and DP

[update] The extended catchment in brown below may be less than shown above  accurate – see The Upper Lye Valley – Headington’s Secret Garden

 The western fen now dies as its remaining, reduced flows are now almost wholly absent as shown in the Post-Development Diagram above.

Policy and Advice

Groundwater protection zones are not fully mitigated by the use of SUDS therefore development within these areas must be restricted or eliminated.Thus development must be restricted or eliminated on Southfield Golf Course East in order to protect the South SSSI and development must be restricted or eliminated within the buffer areas indicated in Tables 5 and 6 to protect the Lye and Boundary Brook riparian corridors. [Pre-EIA, p39]

Catchment Protection Zones

Normally the groundwater protection zone would coincide with the catchment protection zone. The use of SUDS should be compulsory within a catchment protection zone. Figure 6 shows the surface water catchment zone. [Pre-EIA, p39]

Policy G2 of the Emerging Local Plan 2020

Sites and species important for biodiversity and geodiversity will be protected. Planning permission will not be granted for any development that would have an adverse impact on sites of national or international importance (the SAC and SSSIs), and development will not be permitted on these sites, save where related to and required for the maintenance or enhancement of the site’s importance for biodiversity or geodiversity. Development proposed on land immediately adjacent to the SSSIs should be designed with a buffer to avoid disturbance to the SSSIs during the construction period.

 On sites of local importance for wildlife, including Local Wildlife Sites, Local Geological Sites and Oxford City Wildlife Sites, on sites that have a biodiversity network function, and where there are species and habitats of importance for biodiversity that do not meet criteria for individual protection, development will only be permitted in exceptional circumstances whereby:

  1. a) there is an exceptional need for the new development and the need cannot be met by development on an alternative site with less biodiversity interest; and
  2. b) adequate onsite mitigation measures to achieve a net gain of biodiversity are proposed; and where this is shown not to be feasible then compensation measures will be required, secured by a planning obligation.

Conclusion – Key Points

  • The developments will be probably fatal to the Lye Fen
  • No examination has ever been done of the effects of these developments on the hydrology of the Lye
  • The developments are directly contrary to emerging policy G2 and the advice of the Pre-EIA report[1]to stop development in the Lye catchment
  • Any further investigation of the hydrology should be performed by a fresh pair of eyes, not Peter Brett and Associates

Acknowledgements

This submission is a synthesis of many inputs and much work from numerous persons, in particular from the Friends of Lye Valley (FOLV), I do not claim it as my own work, any errors or omissions are entirely the author’s who has never lifted a finger to assist in the Lye, nor is member of the FOLV.

Much is based on the Pre-EIA report, however any misinterpretations or incorrect conclusions are the author’s alone.

References

[1] Investigation of the possible hydrological effects on the Lye Valley Sites of Special Scientific Interest and the riparian zones of the Lye and Boundary Brooks as a result of development on Southfield Golf Course, A Pre-EIA Assessment, Oct 2007, Dr Curt Lamberth Code: Pre-EIA

[2] Plan of Thames Water Drainage (Thames Water)

[3] Oxford Housing Association Report On Phase 1 Desk Study and Phase II Investigation at 2 Dynham Place (REPORT_ON_DESK_STUDY_AND_SITE_INVESTIGATION_ 1.tiff) Code: GIS-1

[4] Oxford Housing Association Report On Phase 1 Desk Study and Phase II Investigation at 2 Dynham PlaceAppendices (REPORT_ON_DESK_STUDY_AND_SITE_INVESTIGATION_ 23.tiff) Code: GIS-2

[5] Town Furze Estate Plan 1954, Oxford City Council Code: Plan1954

[6] Land Quality Assessment, Land East Of Warren Crescent July 2018, WSP Code: WSP LQA
Baseline Hydrogeological Report Feb 2019, WSP, Code: WSP Base

[7] Technical Note Ecology, SUDS and Groundwater Quality 2015 Final , Peter Brett Code: PBA Final

The Author

Mark
Headington Heritage, A personal blog
 
Visit  : www.headingtonheritage.org.uk
Email: headingheritage@outlook.com

Follow me on Twitter: @headingheritage 

Version 1.0 Release: 05/04/20

Version 1.1 Release: 04/07/20 – Updated refs to Girdlestone Gully to Upper Lye and refs to new article.