This stream allows you to develop maps and reports to identify where Designated Sites at Risk of Diffuse Agricultural Pollution and their associated catchments reside. This information will prove a useful indicator in identifying whether resource protection measures available through ES may be appropriate in the vicinity of these sites, although other information may also be required to support this. Please note also that Priority Catchments and designated sites at risk from diffuse agricultural pollution are preliminary, and only indicative of the hydrological catchments draining into designated sites, as defined by data describing the surrounding terrain. They are subject to change and improvement.

The first step when setting up the Priority Catchments stream is to choose your Primary Information layers, which for this stream, is a selection from Priority Catchments and/or Designated Sites at Risk of Diffuse Agricultural Pollution. By default both of the information layers will be selected, but you must continue with a selection from at least one of these options.

Priority Catchments

These areas are derived from the designated sites in to which they drain. Most drain in to SSSIs, a few drain in to SACs. As some sites are within the catchments of other sites, so the Priority Catchments for those sites will be nested one within another.

Priority Catchments were defined using a software tool for MapInfo that generates hydrological catchments based on topographic height data. The height data used was extracted from Ordnance Survey's Profile product, using height points sampled at every 50m (ie every fifth point in the Profile 10m grid). All depressions in the DEM were assumed to be data errors and filled to the level at which they drain out to the surrounding land. Catchments outlet points were generated from the vectors describing the boundaries of the designated sites at risk from diffuse agricultural pollution. In this way, the catchments reflect an approximate definition of the land area draining in to an entire designated site.

A few neighbouring catchments show areas that overlap, ie areas draining simultaneously in two different directions. These areas indicate the preliminary and approximate nature of the data, and the overlaps are likely to be caused by either errors in the underlying data, the sampling methodology used to extract elevation points from that data, or the interpretation of that data by the software tool used to define the catchment polygons. We aim to improve the definition of these catchments in the future to correct such errors.

Designated sites at risk from diffuse agricultural pollution

These sites are listed in English Nature Research Report No. 551 (click here to get a copy). The boundaries displayed in Nature on the Map are the current version of the site boundaries as maintained by the SuperSite database and displayed in the other maps, although during the original study and the process of defining Priority Catchments, an older version of these site boundaries would have been used.

The Designated Sites at Risk of Diffuse Agricultural Pollution relate to those sites listed in English Nature Research Report No. 551 (http://www.naturalengland.org.uk/publications/publications/default.aspx) and are thematically mapped according to their priority status. They are Statutory Designated water-dependent sites considered to be most at risk from, or impacted by, diffuse agricultural pollution. The Priority Catchments layer is indicative of the hydrological catchments draining into designated sites at risk from diffuse agricultural pollution, as defined by data describing the surrounding terrain. More details about these layers can be found in What's in the Targeting and Planning Map? Information relating to either of these information layers is made available to you through the Information Tool.

Once you have selected one or both of these layers for your map, you can if you wish select a BAP Priority Habitat layer to be displayed. This will display the locations within England of rare or threatened semi-natural habitats that are part of the UK Biodiversity Action Plan.

You can also add one or two designated sites layers to the map. The types of sites that you can select are Sites of Special Scientific Interest (SSSIs), National Nature Reserves (NNRs), Local Nature Reserves (LNRs), Special Areas of Conservation (SACs), Special Protection Areas (SPAs) and Ramsar Sites.

The first two are the same sites as appear on the Nature Reserves and Country Parks Map and the Sites of Special Scientific Interest Map. SACs are European protected sites for species and habitats. SPAs are European protected sites for birds. Ramsar sites are internationally designated sites for their import wetland habitats for wildfowl.

<< Back to the Map Types page