CB LNR Reedbed Conservation Project Circulated in August 2018

Appendix 1: Consultation Document

Circulated in August 2018



Cromwell Bottom Wildlife Group (CBWG) and Calderdale Council (CC) are working in collaboration to facilitate the conservation and enhancement of the lagoon and its associated reedbed. This paper aims to provide some background information, to identify the objectives of the project, and to present an overview of the proposals to date for the work to be undertaken. If you have any questions, or wish to make comments about Phase 1, or indeed other parts of the project, please contact members of the project partnership before 04/09/2018 using one of the following e-mail addresses:    countryside@calderdale.gov.uk        cromwell.reedbed@gmail.com


The lagoon and reedbed at Cromwell Bottom Local Nature Reserve are present due to earlier excavation on the site for the extraction of gravel. The depression created was used to deposit pulverised fuel ash (PFA) from the nearby Elland power station. Some of this ash was then removed for use in road construction, leaving basins, one of which is now occupied by the lagoon and reedbed. This basin currently forms part of a flood alleviation washland. It has for some time contained the invasive plant Crassula helmsii (New Zealand pigmyweed).

The lagoon represents the largest area of open water on the Reserve. It relies largely or probably exclusively on rainwater for its continued existence. Reedbeds are one of the rarest habitats in the UK, and are of high conservation value. The one located at Cromwell Bottom is unique within Calderdale. In addition to their ecological importance, those who visit the Reserve agree that the lagoon and reedbed are of major aesthetic value.

The wet woodlands lying immediately to the west and to the east of the lagoon basin also constitute uncommon and very valuable habitats.

Reedbeds, if left undisturbed, are ephemeral, and will undergo a natural succession from open water, through reedbeds that permanently contain standing water, reedbeds that have water levels at or below the ground surface for some or all of the year, to scrub made up mainly of alder and willow that may be wet in winter (carr woodland). Each of these successional habitats (and in some cases the transition zones between them) is ecologically valuable. Ultimately this succession will lead to the drying out and terrestrialisation of the site, and its coverage by climax woodland communities. At Cromwell Bottom, each of these successional stages is present, but it is evident that the area of open water is decreasing, that the reedbed is drying out, and that the proportion of the site made up of carr woodland (much of which also contains birch) is increasing.

Over recent years, attempts have been made to slow the rate of the successional changes by cutting and clearing the reed on a rotational basis, and by coppicing much of the carr woodland.

Objectives of the conservation project

  • To evaluate the existing wildlife value of the lagoon and reedbed.
  • To rehabilitate the lagoon and reedbed by interrupting, and in some cases reversing the natural successional changes.
  • To reduce any detrimental effects on the existing wildlife as much as possible.
  • To avoid any damage to the wet woodlands to the east and west of the lagoon basin, and, if possible, to enhance these habitats as a by-product of the reedbed rehabilitation.
  • To enhance the public amenity value of the Reserve by, for example, developing new and improved viewing areas around the lagoon basin.

Evaluation of the lagoon and reedbed

  • Members of the project partnership are aware of the ecological importance of the lagoon and reedbed, especially for resident, migratory, and nesting birds; amphibians (smooth and palmate newts, common toads, and common frogs); and invertebrates.
  • A survey to detect the presence of water voles was carried out by CBWG members in 2017. No evidence of these mammals was found.
  • A basic survey of the flora was undertaken by a member of the Halifax Scientific Society in 2017. No priority species were identified.
  • CC commissioned an invertebrate survey, which was carried out in 2017 by Richard Wilson Ecology. The survey area also included part of the western wet woodland.  The final report supported the proposed habitat intervention works for the lagoon basin.

Approaches to rehabilitating the lagoon and reedbed

  • The principal techniques for rehabilitation of a reedbed are i) removal of all or part of the scrub, ii) bed lowering, and iii) raising the water levels.
  •  The proposal for this project is to use a combination of these approaches; the works to be carried out in phases as funds become available.

Proposals for the rehabilitation work

Phase 1 – Removal of all or part of the scrub:

  • The majority, or possibly all of the scrub located along the northern side of the lagoon basin (the side nearest to the canal) to be grubbed out, and the resultant area to be excavated to create deep water.
  • The materials removed during grubbing and excavation to be used to build islands (possibly two) designed to attract eg terns and little ringed plover. (No excavated material can be removed from the lagoon basin because of the presence of the pigmyweed.)
  • Grubbing and excavation to be undertaken by professional contractors with considerable experience of working on nature reserves.
  • Stabilisation of the islands to be undertaken, possibly using ‘Aqualogs’ and brushwood fascines.
  • Phase 1 to be undertaken in late September or October of 2018. (This is possible because the CBWG Trustees have offered up to £8K for the completion of this phase.)
  • Help by volunteers to be welcomed, especially with the creation of the final structure of the islands.

Later phases – Raising the water levels:

  • The ground level under the bridge on the eastern bund to be lowered, and a stop log (drop board) sluice to be installed at this location. This will allow the desired new water levels to be maintained/controlled.
  • Water to be brought into the lagoon basin to reach and maintain the desired levels by either i) pumping water from the River Calder, or ii) extracting water, using gravity, from the Calder and Hebble Navigation.
  • If possible, some water settling and/or filtration to be enabled between its extraction and its entry into the lagoon basin.
  • If possible, the imported water to be used appropriately to help to re-wet the eastern and western wet woodlands.

Subsequent management and monitoring:

  • The water levels to be managed carefully and appropriately over each twelve month cycle.
  • The reeds to continue to be cut and processed on site on a rotational basis.
  • Any carr woodland that may remain to be coppiced appropriately.
  • The lagoon basin flora and fauna to be monitored for at least two years following the interventions.

How the proposed rehabilitation work has been/is being planned

To date, this has included:

  • Creation, at the outset, of a project steering group comprising representatives of CBWG and of CC.
  • Reference to appropriate literature, eg

Friends of Cromwell Bottom (2002) Cromwell Bottom: A Natural and Unnatural History.

JBA Consulting (2005) Water Level Management at Cromwell Bottom: Feasibility Assessment Final Report.

MRB Ecology and Environment (2005) Cromwell Bottom Biodiversity Restoration Project: Water Level Feasibility Study Hydro-ecological Assessment Final Report.

Richard Wilson Ecology (2017) Terrestrial Invertebrate Survey, Cromwell Bottom Nature Reserve, nr. Brighouse, West Yorkshire.

Hawke, C. J. & Jose P. V. (1996) Reedbed Management for Commercial and Wildlife Interests. Sandy: RSPB.

Williams, P., Biggs, J., Whitfield, M., Thorne, A., Bryant, S., Fox, G. & Nicolet, P. (2010) The Pond Book: A Guide to the Management and Creation of Ponds.2nd ed. Oxford: Freshwater Habitats Trust.

White, G., Self, M. & Blyth, S. (2014) Bringing Reedbeds to Life: Creating and Managing Reedbeds for Wildlife. Sandy: RSPB.

  • Consultation with representatives of the Environment Agency.
  • Visits to Carlton Marsh Nature Reserve (to discuss their recent reedbed rehabilitation project), and to Rodley Nature Reserve (to discuss their irrigation system using water abstracted from the River Aire).
  • Advice provided during site visits to the lagoon basin by i) Dr Tony Vann (retired senior lecturer in ecology at the University of Huddersfield, whose research interests included restoration of ex-industrial sites in Yorkshire, and studies of PFA); and ii) Pete Wall (Dearne Valley Living Landscape Manager with Yorkshire Wildlife Trust, who played a major role in the rehabilitation project at Carlton Marsh).
  • The gathering of advice and information from various commercial sources.
  • Commissioning of a costed scheme proposal for the installation of a sluice and for the means of pumping water from the river.
  • Consultations with the Canal and River Trust’s Head of Commercial Water Development regarding the possibility of abstracting water from the canal.
  • Informal discussions with visitors to the Reserve, including those with special ecological interests and expertise.
  • A number of site walks and planning meetings.

Thank you so much for your interest in this project.