Identification

Title

Sefton Flood Risk Areas 1 in 30year model

Abstract

The Environment Agency estimates that 200,000 homes in the North West are at risk from flooding, Sefton Council takes this risk seriously, having suffered severe surface water flooding a number of times since 1990 with significant flooding events occurring in 2001, 2004, 2008, 2010 and 2012. In addition, parts of Sefton are influenced by shallow groundwater and a fluvial flood risk that is currently managed by pumping. These factors make Sefton sensitive to the effects of climate change. In order to address some gaps in understanding from previous Merseyside Flood Management Plans, Sefton Council, in partnership with the Environment Agency, Capita Symonds and United Utilities developed a Surface Water Management Plan (2011). Alongside the SWMP a Strategic Risk Assessment was produced, this applied a risk based approach to spatially identify urban and highly developed areas at most risk from flooding. Hydraulic modelling was undertaken of both sewer flooding and surface water flooding for storm events with a 1 in 30 (3.3%), 1 in 100 (1%) and 1 in 100+cc (1%+cc) chance of occurring in any given year, cc represents a climate change factor. This data is the 1 in 30 (3.3%) model. The impacts of climate change were also considered by increasing rainfall intensity by 30%. The SWMP models were updated to include new information in 2013. The models have been constructed for the purpose of assessing surface water flood risk in Sefton. This modelling was undertaken by Capita Symonds using ESTRY-TUFLOW software version 2012-05-AE. Each model has been built upon a 5m cell size and simulated using the software. The drainage network has not been explicitly modelled however it has been represented by applying a continuing loss to impermeable land uses. The modelled outputs were based on flood velocity, depth and hazard, a debris factor was used in calculating hazard rating e.g. debris factor of 0.5 for depths,=0.25 and 1 for depths>0.25, based on DEFRA’s guidance methodology, for further details please reference DEFRA’s Flood Risks to People Phase 2 – FD2321/TR1. The Environment Agency estimates that 95% of all flood damage occurs during the first 23 cm of external floodwater. In order to assess the potential damage to property in Sefton, the models used an impact based on there being a depth of flooding at each property of at least 0.08m to produce the flood outlines. However, because of the way in which buildings are represented, this equates to a flood depth around the building of 0.23m. (i.e. the mean flood depth is simulated to exceed 80mm inside the property, which is equivalent to 230mm externally). The GIS data has been checked for geographic errors and is accurate.

Resource type

dataset

Resource locator

http://inspire.misoportal.com/geoserver/sefton_council_sefton_flood_risk_areas_1_in_30year_model_polygon/wms?request=getCapabilities

name: INSPIRE View Service

function: information

http://misoportal.com/portal/api/request-licenced-data/1753

name: INSPIRE Download Service

function: download

Unique resource identifier

code

Sefton Flood Risk Areas 1 in 30year model

codeSpace

unknown

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

environment

Keywords

Keyword set

keyword value

Natural risk zones

originating controlled vocabulary

title

GEMET - INSPIRE themes, version 1.0

reference date

date type

publication

effective date

2008-06-01

Keyword set

keyword value

Flood Risk Areas, Local Flood Risk, hydrological

Geographic location

West bounding longitude

-3.3518600332

East bounding longitude

-2.6789474355

North bounding latitude

53.7992314367

South bounding latitude

53.3753412768

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

creation

effective date

2011-05-16

date type

publication

effective date

2011-08-01

date type

revision

effective date

2013-07-01

Frequency of update

asNeeded

Quality and validity

Lineage

Data created by Capita Symonds for Sefton Council in partnership with the Environment Agency and United Utilities. Data was collected and reviewed in order to map broad areas vulnerable to surface water flooding, research included historic flood records, fluvial and tidal, surface water flooding events, ground water flooding and sewers, drains, ditches and watercourses. Maps created using 500m grids.

Conformity

Data format

name of format

unknown

version of format

unknown

Constraints related to access and use

Constraint set

Limitations on public access

This data can only be accessed under the PSMA INSPIRE End User Licence terms.

Constraint set

Use constraints

This data may only be accessed under the PSMA INSPIRE End User Licence terms.

Responsible organisations

Responsible party

contact position

Flood & Coastal Erosion Risk Management Team Leader

organisation name

Sefton Metropolitan Borough Council

full postal address

SEFTON MBC Flood & Coastal Erosion Risk Management Locality Services Division Department of Built Environment 3rd Floor Magdalen House 30 Trinity Road

Bootle

L20 3NJ

United Kingdom

telephone number

0845 140 0845

email address

Flooding@sefton.gov.uk

web address

https://www.sefton.gov.uk

responsible party role

owner

Metadata on metadata

Metadata point of contact

contact position

Flood & Coastal Erosion Risk Management

organisation name

Sefton Metropolitan Borough Council

full postal address

SEFTON MBC Locality Services Division Department of Built Environment 3rd Floor Magdalen House 30 Trinity Road

Bootle

L20 3NJ

United Kingdom

telephone number

0845 140 0845

email address

Flooding@sefton.gov.uk

web address

https://www.sefton.gov.uk

responsible party role

pointOfContact

Metadata date

2015-11-12T08:55:17

Metadata language

eng