Risk of Flooding from Surface Water
The surface water flood maps give an indication of the broad areas likely to be at risk of surface water flooding. This includes flooding that takes place from the surface runoff generated by rainwater (including snow and other precipitation) that: (a) is on the surface of the ground (whether or not it is moving), and (b) has not yet entered a watercourse, drainage system or public sewer. The Flood Map for Surface Water pick out natural drainage channels, rivers, low areas in floodplains, and flow paths between buildings. But it does not indicate flooding caused by local rainfall. It does not show flooding that occurs from overflowing watercourses, drainage systems or public sewers caused by catchment-wide rainfall events or river flow. A national model has been run for 1 in 30, 1 in 100 and 1 in 1000 year rainfall events. It has been modelled on a 2 metre square grid. Lead Local Flood Authorities were consulted and where available locally held model outputs have been incorporated into the maps. This dataset has been superseded by the new National Flood Hazard Maps 2019 - NRW_DS124790
- Identification
- Extent
- Distribution
- Quality
- Keywords
- Spatial Reference System
- Content
- Constraints
- Maintenance
- Metadata
Identification
- Identifier
- NRW_DS116273
- Alternative Title
-
- Surface Water Flood Risk 1000.LYR
- Surface Water Flood Risk 100.LYR
- Surface Water Flood Risk 30.LYR
- Risk of Flooding from Surface Water
- AfA375 Updated Flood Map for Surface Water Complex Package
- Map Llifogydd a Ddiweddarwyd ar gyfer Pecyn Sylfaenol Dŵr Arwyneb
- Metadata Language
- English
- Lineage
-
The Flood Map for Surface Water is in vector (polygon) format and includes the following component layers: 1. EXTENTS - three layers showing extent of flooding for three separate probabilities : 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 2. DEPTHS - three banded layers showing depth of flooding for three separate probabilities: 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 3. VELOCITY - three banded layers showing flooding velocity for three separate probabilities: 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 4. HAZARDS - is the Hazard rating and is a function of depth and velocity for the particular scenario using the Hazard Rating formula HR = d x (v + 0.5) + DF where HR is hazard rating, d is depth, v is velocity and DF is a debris factor. 5. FLOW DIRECTION (25m) - three banded layers showing flood flow direction (at maximum velocity) for three separate probabilities: 1 in 30, 1 in 100 and 1 in 1000 (created from resampled 25m raster grid) 6. SUITABILITY - one layer showing basic confidence information from the modelling which gives an indication of the scale at which is it generally appropriate to use this information to assess flood risk and parameters used. This dataset is not suitable for identifying whether an individual property will flood. Because of the way they have been produced and the fact that they are indicative, the maps are not appropriate to act as the sole evidence for any specific planning or regulatory decision or assessment of risk in relation to flooding at any scale without further supporting studies or evidence.
- Additional Information
-
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/297432/LIT_8988_0bf634.pdf
- Dataset Reference Date (Publication)
- 2016-10-17
Extent
Extent
- Geographic Extent
- Wales (WLS)
))
Distribution
- Format Type and Description
-
-
Geographic Information System
()
- Specification
-
ESRI Geodatabase
-
Geographic Information System
()
Quality
Data quality
- Quality Scope
- Dataset
- Lineage
-
The Flood Map for Surface Water is in vector (polygon) format and includes the following component layers: 1. EXTENTS - three layers showing extent of flooding for three separate probabilities : 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 2. DEPTHS - three banded layers showing depth of flooding for three separate probabilities: 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 3. VELOCITY - three banded layers showing flooding velocity for three separate probabilities: 1 in 30 (high risk), 1 in 100 (medium risk) and 1 in 1000 (low risk) chance of flooding in one year, 4. HAZARDS - is the Hazard rating and is a function of depth and velocity for the particular scenario using the Hazard Rating formula HR = d x (v + 0.5) + DF where HR is hazard rating, d is depth, v is velocity and DF is a debris factor. 5. FLOW DIRECTION (25m) - three banded layers showing flood flow direction (at maximum velocity) for three separate probabilities: 1 in 30, 1 in 100 and 1 in 1000 (created from resampled 25m raster grid) 6. SUITABILITY - one layer showing basic confidence information from the modelling which gives an indication of the scale at which is it generally appropriate to use this information to assess flood risk and parameters used. This dataset is not suitable for identifying whether an individual property will flood. Because of the way they have been produced and the fact that they are indicative, the maps are not appropriate to act as the sole evidence for any specific planning or regulatory decision or assessment of risk in relation to flooding at any scale without further supporting studies or evidence.
Keywords
Keywords
- Type
- Theme
Citation
- Date (Publication)
- 2008-06-01
Keywords
Keywords
Keywords
-
NRW SMNR Vocabulary
-
- Natural Resources (incl. Features and Processes) (SMNR)
- Ecosystem (SMNR)
- Flooding (SMNR)
- Hydrological Processes (SMNR)
- Sustainable Management of Natural Resources (SMNR)
- Management Areas (SMNR)
- Freshwater and Wetlands (SMNR)
- Sea and Coast (SMNR)
- Soil and Land (SMNR)
- Physical Geography (physiography) (SMNR)
- Type
- Theme
Citation
- Date (Revision)
- 2023-12-27
Spatial Reference System
Content
Content Information
NRW Profile
Custom Elements
- NRW Related Title
-
National Flood Hazard Maps 2019
Constraints
Constraints
Limitations on Public Access and Use
- Restriction type
- Other restrictions
Access Constraints Directive
- Limitations
- no limitations
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 and Centre for Ecology and Hydrology © NERC (CEH) Some features of this information are based on digital spatial data licensed from the Centre for Ecology and Hydrology © NERC (CEH). Defra, Met Office and DARD Rivers Agency © Crown copyright. © Cranfield University. © James Hutton Institute. Contains OS data © Crown copyright and database right 2015. Land and Property Services © Crown copyright and database right. 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.
Metadata
Metadata
- File Identifier
- 4f4c4942-4343-5764-6473-313136323733 XML
- Metadata Language
- English
- Resource type
- Dataset
- Metadata Date
- 2024-05-30T15:17:18.388Z
- Metadata Standard Name
- NRW
- Metadata Standard Version
-
1.0