Dalgylchoedd dŵr croyw ACA morol sydd angen niwtraliaeth nitrogen
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 25th July 2025 and maybe subject to future changes.
Please also see metadata entry NRW_DS161370 "Nutrient Sensitive Marine SAC Freshwater Catchments".
- Dull adnabod
- Rhychwant
- Dosbarthiad
- Ansawdd
- Allweddeiriau
- System Cyfeirio Gofodol
- Cynnwys
- Cyfyngiadau
- Cynnal a chadw
- Metadata
Dull adnabod
- Dynodydd
- NRW_DS161371
- Teitl Amgen
-
- Marine SAC freshwater catchments requiring nitrogen neutrality.lyr
- Laith Metadata
- English
Llinach
- Datganiad
-
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 Govt 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 TraC 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.
- The Nutrient sensitive Marine SAC freshwater catchments layer still has some areas of flat coastal drainage that needs further data processing e.g. the boundary between the Dee and the Clywd freshwater catchments, and the boundary between Kenfig SAC and Port Talbot (Swansea Bay coastal WB).
- Gwybodaeth ychwanegol
-
Marine SAC condition assessments published on NRW website:
- Dyddiad cyfeirnod y set ddata (Creu)
- 2025-07-31
Ystod amser
- Dyddiad cychwyn
- 2025-01-16
- Categori pwnc
-
- Environment
))
Dosbarthiad
- Fformat - Math a Disgrifiad
-
-
Geographic Information System
(
Unknown
)
- Math
-
ESRI Feature Class
-
Geographic Information System
(
Unknown
)
Ansawdd
Ansawdd Data
- Cwmpas Ansawdd
- Dataset
- Cydymffurfiad
- 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
- Eglurhad
-
This dataset has not been assessed for conformance to the referenced INSPIRE regulation.
- Gradd
- false
Llinach
- Datganiad
-
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 Govt 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 TraC 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.
- The Nutrient sensitive Marine SAC freshwater catchments layer still has some areas of flat coastal drainage that needs further data processing e.g. the boundary between the Dee and the Clywd freshwater catchments, and the boundary between Kenfig SAC and Port Talbot (Swansea Bay coastal WB).
Allweddeiriau
Allweddair
Allweddair
-
NRW Thesaurus
-
- MARINE
- protected sites
- FRESHWATER
- Special Areas of Conservation (SAC) (see also Candidate Special Areas of Conservation cSAC)
- Math
- Theme
Dyfyniad
- Dyddiad (Cyhoeddiad)
- 2025-01-08
Allweddair
-
SeaDataNet Parameter Discovery Vocabulary
-
- Unspecified
- Math
- Theme
Dyfyniad
- Dyddiad (Cyhoeddiad)
- 2024-06-19
System Cyfeirio Gofodol
Cynnwys
Gwybodaeth Cynnwys
Proffil CNC
Elfennau CNC
Cyfyngiadau
Cyfyngiadau
Cyfyngiadau ar Fynediad a Defnydd Cyhoeddus
- Math o Gyfyngiad
- Other restrictions
Testun cyfyngiadau mynediad
- Cyfyngiadau eraill
-
Access restrictions on this data have not been determined. It may contain sensitive information and therefore may be restricted under legislation. NRW may provide access to this dataset on request, however NRW may not release, publish or disseminate the data or derived products freely without further assessment.
Defnyddiwch gyfyngiadau
- Cyfyngiadau Defnyddio
- Other restrictions
- Cyfyngiadau eraill
-
© 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 only be re-used externally under provision and in line with the terms of a NRW licence following an assessment of the data.
Datganiad Priodoli
- Cyfyngiadau eraill
-
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.