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Leam Catchment Tree Planting Project (2013-) The Leam catchment covers an area of 360km2 and includes five main waterbodies – the River Leam, River Itchen, River Stowe, and the Rains and Radford Brooks. Monitoring of the catchment’s waterbodies for the Water Framework Directive showed them to fail in several areas. The key issues preventing them achieving Good Ecological Status involved phosphates, pesticides and sedimentation, mainly caused by runoff from industrial, agricultural and domestic land. The causes of the problem include livestock heavily poaching riverbanks and damaging riparian vegetation with poor structure, which resulted in large quantities of sediment entering the river. Cattle poachingCattle poaching has led to the removal of riparian vegetation and allows large amounts of sediment and bound phosphate to enter the river. Four farms in the catchment were identified as contributing to issues of water quality. Melissa Hoskings, the local Catchment Officer, identified the four farms through her Catchment Sensitive Farming visits.  Melissa spoke with each of the farmers about the poached banks and advised on fencing as a method to limit further soil erosion and loss of valuable top soil and to also reduce sedimentation of the river.  Tree planting in these areas was also advised which would help to maintain the structure of the bank, whilst also providing valuable shading for the river during the summer, habitat for wildlife, and act as a buffer to reduce the amount of phosphate entering the watercourse. Tree solutions In March 2013, with funding from the Woodland Trust, the project planted 3,515 native broadleaf trees, covering 10 hectares, of local provenance along the banks of watercourses and across the above four farms in the catchment. Fencing and tree planting to create bufferTree planting along the banks of the River Itchen provides a wealth of benefits to the aquatic environment.   Riparian fencing was also erected using funding from the Environment Agency. This restricts livestock access to the waters’ edge and reduces the risk of them damaging the newly planted trees. Tree species planted at each site and the associated percentage mix:

% mix
oak (Quercus Robur) 10%
alder (Alnus Glutinosa) 10%
crab apple (Malus sylvestris) 10%
hazel (Corylus Avellana) 10%
field maple (Acer Campestre) 10%
blackthorn (Prunus spinosa) 5%
hawthorn (Crataegus Monogyna) 5%
spindle (Euonymus europeus) 5%
willow (Salix alba) 10%
black poplar (Populus nigra) 10%
aspen (Populus tremula) 10%
hornbeam (Carpinus betulus) 5%

The benefits of tree planting include:

  • Binding the banks together and reducing levels of sediment entering the river and covering river gravels used for spawning fish.
  • Reducing influx of sediment will benefit macrophytes.
  • Improving substrate composition will subsequently provide benefits for macroinvertebrates and phytobenthos.
  • Reducing volumes of phosphate entering the rivers locked to soil particles.
  • Increasing shade to help reduce water temperatures and increase dissolved oxygen levels.
  • Increased shading will also provide long-term benefits to the waterbodies by helping to relieve the effects of climate change.
  • Reducing light levels through shading will reduce periphyton accrual rate and help to reduce the risk of eutrophication.
  • Holding the soil structure together to allow pesticides to be absorbed into soil and degraded naturally.
  • Allow the natural development of riparian vegetation, which will subsequently provide shelter for juvenile fish, a habitat for macroinvertebrates and phytobenthos, and help to “clean” the water.

This project is an ongoing partnership with the Woodland Trust. If you are a land owner in the Severn Rivers Trust area and are interested in tree planting then please get in touch with Melissa Hoskings.