The River Ouse Project

About

There are three strands to the project: botanical survey linked to historical research; grassland enhancement field trials; and grassland enhancement projects.

Please expand the headings below for further information. 

A washland flood alleviation strategy

A flooded field near Horsted KeynesA flooded field near Horsted Keynes

The Sussex Ouse has a wide catchment with a large number of small streams. After heavy and prolonged rain increased flow in these streams leads to a rapid rise in water level downstream with potentially disastrous consequences as in 2000 when Uckfield and Lewes flooded. Flood alleviation depends on holding back the water temporarily in the upper regions until water from lower down the system has passed through. In the past, peak flow resulted in water spilling out onto ‘washland’ in the upper reaches, ameliorating flooding lower down. Navigation works between 1790 and 1799 on the main Ouse and the deepening of Ouse streams in the 1970s to drain agricultural land have reduced the amount of land subject to this temporary flooding and this, combined with the ploughing up of species-rich grassland which absorbed rainwater, has led to increased flood risk in towns downstream. The washlands on the river Ouse typically flood for 2-3 days and we use the term ‘flash’ washlands to distinguish these from the washlands on the Cambridgeshire Ouse which stay flooded for several months.

Species-rich grassland is a Biodiversity Action Plan plant community and so it is a win-win situation that conservation of this rare habitat can be linked to flood alleviation. 

Ecological survey linked historical research

cows in Caseford BottomStreamside meadow near Horsted Keynes

 

Detailed ecological survey of streamside habitats (led by Dr Margaret Pilkington) is being combined with historical studies to understand the distribution of species-rich sites and to identify the best sites for woodland re-creation or grassland enhancement schemes linked to flood alleviation. Results are being written up in a series of reports (see Project reports on website for downloadable pdf). Documentary historical research (led by Dr Will Pilfold) is being supplemented by oral history interviews with key respondents who can recall details of land use and human impact that are not available through archive sources. The first two years of the project were funded by a Leverhulme Research grant which paid for a full-time oral historian (Dr Andrew Holmes). Since then oral history interviews have been conducted by continuing education volunteers.

Botanical survey of streamside habitats

Volunteer surveyors at workVolunteer surveyors at work

 

Botanical survey work which began in 2006 takes place each summer. Continuing education volunteers are surveying streamside woodland and grassland in the Upper Ouse. Data from grassland and wet woodland habitats are analysed using the National Vegetation Classification system to develop an understanding of the composition of species-rich sites and their role in flood alleviation. Many of the streams have steep-sided wooded valleys (gills) which are being surveyed using a series of 30m lengths of stream valley. A new descriptive system for classifying gills is being developed and a prototype is used in the Project Reports.

Washland meadow restoration

CCE volunteers sowing wildflower seed at Buckham Hill Brooks, November 2011CCE volunteers sowing wildflower seed at Buckham Hill Brooks, November 2011

In collaboration with the Sussex Wildlife Trust (Sussex Wetland Landscapes Project), Kew at Wakehurst, Weald Meadows Initiative and local landowners restoration work was begun in 2011 on 20 hectares of washland along the upper Ouse. 

Wildflower seed collected by Kew and stored in the seed-bank at Wakehurst was used to grow 6000 plugs which were then planted into 0.5ha areas at 4 washland sites. Weald Meadows Initiative seed was also sown.  It was specified that the sites should be grazed (preferably by cattle) for the following 2 years and then managed as hay meadows. The flower-rich area was to be extended by green hay spreading year by year: a technique shown to be successful at Home Farm Herons Ghyll where we monitored the spread of flower-rich grassland across a species-poor field between 2006 and 2011. Management prescriptions, however, were followed at only one site (Buckham Hill) where botanical survey in 2015 demonstrated successful conversion to species-rich MG5a grassland. The other sites only served to demonstrate that without appropriate management over a number of years wildflowers are unlikely to establish successfully.







Grassland enhancement field trials

 

cowslip in field trialcowslip in field trial December 2009 surrounded by floodwater silt

The first field trial was set up in the upper Ouse catchment to determine an effective method for increasing the plant biodiversity of grassland, so that good use could be made of expensive wildflower seed or plant-plugs on those sites identified by ecological survey and past land-use as suitable for grassland enhancement combined with flood alleviation. The site was subjected to pre-experiment treatment to reduce the grass cover and open up bare ground for colonisation by wildflower species. In September 2007, plant plugs of nine species of wildflower were planted into 4 plots and 4 other plots were sown with seed of the same wildflower species. Four control plots compared both these options with unaided colonisation of species following the pre-experiment reduction in grass cover. The experiment was monitored by continuing education volunteers, coordinated by Dr Margaret Pilkington. The setting-up costs of the experiment were funded by the Leverhulme Trust.

In October 2007 a repeat field experiment was set up at SheffieldPark on a riverside meadow subject to short-duration flooding. We know from oral history interviews with past tenants that this meadow was full of cowslips until fertiliser was applied in the middle of the last century, so cowslip was one of the ten species of wildflower used in the field trial which was set up along similar lines to the 2007 field experiment. The plant plugs were grown by Kew at Wakehurst using Weald Meadows Initiative seed and the same origin seed was sown in the seed plots. This experiment was monitored by continuing education volunteers, coordinated by Dr Margaret Pilkington. Results are given in Project Report 8: Grassland Enhancement Field Trial in Iron Gates Mead (see Project reports on website for downloadable pdf ).