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 This dataset has been superseded by the new National Flood Hazard Maps 2019 - NRW_DS124790

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

Temporal Extent

Begin date: 2013-03-01

End date: 2013-03-01

Topic category

Environment
Inland waters

Owner

Natural Resources Wales (NRW)

Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales

http://naturalresources.wales/?lang=en

Originator

Environment Agency Wales

Environment Agency Wales, Cambria House, 29 Newport Road, Cardiff, CF24 0TP

http://www.environment-agency.gov.uk/regions/wales

Extent

Geographic Extent: Wales (WLS)

Format Type and Description

Geographic Information System ()

Specification

ESRI Geodatabase

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
Degree: false

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

GEMET - INSPIRE themes, version 1.0

Natural risk zones

Type: Theme

Citation

Date (Publication): 2008-06-01

Code: geonetwork.thesaurus.external.theme.httpinspireeceuropaeutheme-theme

Keywords

NRW Thesaurus

flood modelling

Type: Theme

Citation

Date (Publication): 2023-12-31

Code: geonetwork.thesaurus.local.theme.converted_nrw-keywords

Keywords

Integrated Public Sector Vocabulary

risk management

Type: Theme

Citation

Date (Revision): 2013-04-03

Code: geonetwork.thesaurus.external.theme.subjects

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

Code: geonetwork.thesaurus.local.theme.converted_nrw-smnr-keywords

Code: British National Grid (EPSG::27700)

Content Information

NRW Profile

Custom Elements

NRW Related Title: National Flood Hazard Maps 2019

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

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

pointOfContact

Natural Resources Wales (NRW)

Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales

http://naturalresources.wales/?lang=en

Publishing Body

Access the portal

Full access to the portal and metadata.

Risk of Flooding from Surface Water

Identification

Temporal Extent

Extent

Extent

Distribution

Quality

Data quality

Keywords

Keywords

Citation

Keywords

Citation

Keywords

Citation

Keywords

Citation

Spatial Reference System

Content

Content Information

NRW Profile

Custom Elements

Constraints

Constraints

Limitations on Public Access and Use

Access Constraints Directive

Access Constraints Text

Use Constraints

Metadata

Metadata

Publishing Body