Marine SAC Freshwater Catchments Requiring Nitrogen Neutrality
The Marine SAC Freshwater Catchments Requiring Nitrogen Neutrality layer is a subset of the Nutrient Sensitive Marine SAC Freshwater Catchments layer. It only shows the three freshwater catchments that require nitrogen neutrality based on NRW’s advice letter of 25th July 2025 and maybe subject to future changes.
Please also see metadata entry NRW_DS161370 "Nutrient Sensitive Marine SAC Freshwater Catchments".
- Identification
- Extent
- Distribution
- Quality
- Keywords
- Spatial Reference System
- Content
- Constraints
- Maintenance
- Metadata
Identification
- Identifier
- NRW_DS161371
- Alternative Title
-
- Marine SAC freshwater catchments requiring nitrogen neutrality.lyr
- Metadata Language
- English
Lineage
- Lineage
-
The Nutrient sensitive Marine SAC freshwater catchments layer has been created in QGIS largely using the PCRaster toolset.
Data sources from DataMapWales:
- ‘LIDAR data download’ - comprising Welsh Government LIDAR 2020-2023
- ‘Wales Boundary’ (High Water Mark),
- ‘Wales National Marine Plan Boundary’ - (Normal Tidal Limit) - ‘SACs’
- ‘WFD Cycle 2 TraC Waterbodies’.
All Open Government Data sources.
Data Processing: (QGIS largely using PCRaster toolset)
- Native resolution LIDAR Digital Terrain Model (DTM) geotiff data was resampled at 10m x 10m resolution.
- DTM converted to PC raster format.
- DTM clipped to High Water using Wales (High Water Mark) polygon.
- DEM converted to Local Drain Direction (LDD) raster having filled pits in DTM (using ‘LDDcreate’ tool for both tasks)
- LDD raster processed (using ‘pit’ tool) to identify drainage outlets to the DTM boundary, creating an ‘outlets’ raster.
- LDD and Outlets rasters processed (using ‘catchments’ tool) to create upstream catchments flowing to the outlet points, one for each outlet. Created ‘catchments’ raster.
- Converted Catchments raster to vector format.
Tidying up and adding data attributes:
- The Catchments vector layer was clipped using the National Marine Plan boundary (Normal Tidal Limits) to better represent the land/sea interface and create a closer match with WFD Transitional water body boundaries.
- Catchment polygons were assigned values representing the SAC and WFD Transitional or Coastal waterbody they flowed into, or could directly affect (i.e. where adjacent) – created using the SAC and WFD Cycle 2 WB layers.
Adjustment for Marine SAC nutrient use:
- Catchments (polygons) with common combined Waterbody and SAC values were merged.
Where there was an obvious deviation between the freshwater catchment vector layer and the existing WFD river catchment layer, resulting from man-made interventions viewable on the map data, the freshwater catchment boundary was adjusted to align with the WFD river catchment water body boundary.
- Additional Information
-
Marine SAC condition assessments published on NRW website:
- Dataset Reference Date (Creation)
- 2025-07-31
- Dataset Reference Date (Publication)
- 2025-09-08
Temporal Extent
- Begin date
- 2025-01-16
- Topic category
-
- Environment
))
Distribution
Distribution
- Format Type and Description
-
-
Geographic Information System
(
Unknown
)
- Specification
-
ESRI Feature Class
-
Geographic Information System
(
Unknown
)
- Resource Locator
- Download Data & Web Services ( WWW:LINK-1.0-http--link )
- Resource Locator
- Web Mapping Service ( OGC:WMS )
Quality
Data quality
- Quality Scope
- Dataset
- Conformity
- Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services
- Explanation
-
This dataset has not been assessed for conformance to the referenced INSPIRE regulation.
- Degree
- false
Lineage
- Lineage
-
The Nutrient sensitive Marine SAC freshwater catchments layer has been created in QGIS largely using the PCRaster toolset.
Data sources from DataMapWales:
- ‘LIDAR data download’ - comprising Welsh Government LIDAR 2020-2023
- ‘Wales Boundary’ (High Water Mark),
- ‘Wales National Marine Plan Boundary’ - (Normal Tidal Limit) - ‘SACs’
- ‘WFD Cycle 2 TraC Waterbodies’.
All Open Government Data sources.
Data Processing: (QGIS largely using PCRaster toolset)
- Native resolution LIDAR Digital Terrain Model (DTM) geotiff data was resampled at 10m x 10m resolution.
- DTM converted to PC raster format.
- DTM clipped to High Water using Wales (High Water Mark) polygon.
- DEM converted to Local Drain Direction (LDD) raster having filled pits in DTM (using ‘LDDcreate’ tool for both tasks)
- LDD raster processed (using ‘pit’ tool) to identify drainage outlets to the DTM boundary, creating an ‘outlets’ raster.
- LDD and Outlets rasters processed (using ‘catchments’ tool) to create upstream catchments flowing to the outlet points, one for each outlet. Created ‘catchments’ raster.
- Converted Catchments raster to vector format.
Tidying up and adding data attributes:
- The Catchments vector layer was clipped using the National Marine Plan boundary (Normal Tidal Limits) to better represent the land/sea interface and create a closer match with WFD Transitional water body boundaries.
- Catchment polygons were assigned values representing the SAC and WFD Transitional or Coastal waterbody they flowed into, or could directly affect (i.e. where adjacent) – created using the SAC and WFD Cycle 2 WB layers.
Adjustment for Marine SAC nutrient use:
- Catchments (polygons) with common combined Waterbody and SAC values were merged.
Where there was an obvious deviation between the freshwater catchment vector layer and the existing WFD river catchment layer, resulting from man-made interventions viewable on the map data, the freshwater catchment boundary was adjusted to align with the WFD river catchment water body boundary.
Keywords
Keywords
Keywords
-
NRW Thesaurus
-
- protected sites
- MARINE
- FRESHWATER
- Special Areas of Conservation (SAC) (see also Candidate Special Areas of Conservation cSAC)
- Type
- Theme
Citation
- Date (Publication)
- 2025-01-08
Keywords
-
SeaDataNet Parameter Discovery Vocabulary
-
- Unspecified
- Type
- Theme
Citation
- Date (Publication)
- 2024-06-19
Spatial Reference System
Content
Content Information
NRW Profile
Custom Elements
Constraints
Constraints
Limitations on Public Access and Use
- Restriction type
- Other restrictions
Access Constraints Directive
- Limitations
- noLimitations
Access Constraints Text
- Other constraints
-
There are no access restrictions on this data. NRW may release, publish or disseminate it freely.
Use Constraints
- Use constraints type
- Other restrictions
- Other constraints
-
© CNC/NRW All rights Reserved. Contains Ordnance Survey Data. Ordnance Survey Licence number AC0000849444. Crown Copyright and Database Right. Crown Copyright: Welsh Government. Data may be re-used under the terms of the Open Government Licence providing it is done so, acknowledging both the source and copyright of the owners. It is the recipient's responsibility to ensure the data is fit for the intended purpose.
Attribution Statement
- Other constraints
-
Contains Natural Resources Wales information © Natural Resources Wales and Database Right. All rights reserved. © Crown Copyright and Database Rights. Ordnance Survey Licence number AC0000849444, © Crown Copyright: Welsh Government.
Licence
- Other constraints
- Open Government Licence