Rain gardens for the Day Brook, UK

General

National Id:

United Kingdom_04

Site name:

Day Brook, Nottingham

Summary:

A rain garden was installed along the verges of a residential road in Nottingham, England. The purpose of the rain garden was to control the rate of runoff and water quality reaching the downstream watercourse (Day Brook).

The in-depth description of the case study:

cs-uk-04-final_version.pdf

Location description:

The rain garden is located on a residential street in Nottingham, England. Runoff from the road goes to a small stream called Days Brook.

NUTS Code:

Derbyshire and Nottinghamshire

RBD code:

UK04

Transboundary:

Data provider:

Heather Williams and Katie Hill, AMEC

Source(s):

Nottingham Green Streets †“ Retrofit Rain Garden Project

NWRM(s) implemented in the case study:

Rain Gardens

Longitude:

-1.142012

Latitude:

52.992004

Site information

Climate zone:

cool temperate moist

Mean annual rainfall:

600 - 900 mm

Mean rainfall unit:

mm/year

Average imperviousness:

100

Type:

Actual Test Site

Light or indepth?:

In-depth

Average slope range:

1-2%

Vegetation class:

Predominantly Urban

Monitoring maintenance

Monitoring impacts effects:

Monitoring location:

Unknown

Administrative annual cost information:

Some monitoring is undertaken but no indication of costs has been obtained.

Monitoring parameters:

A data logger was installed beneath two of the rain gardens, which allows continuous water depth recording. This monitoring has taken place between May 2013 and September 2014.

Performance

Performance impact estimation method:

Laboratory

Performance impact estimation information:

Continuous water level monitoring is allowing a short period of data to be collected post-implementation, and will allow future monitoring of any variation in rain garden performance. InfoWorks CS 2D modelling has been undertaken since implementation, to model the anticipated reduction in the flow reaching the sewer based on the data logger information.

Biophysical impacts

Information on increased water storage:

No storage previously

Runoff reduction:

Runoff reduction unit:

% Percent

Information on runoff reduction:

Increased water storage will provide additional capacity to retain and efficiently remove run off from highways, and infiltrate to ground. This will reduce the volume of water reaching the local sewer and Day Brook. Modelled 33% reduction in flow reaching the sewer for 1 in 1 year event

Information on Peak flow rate reduction:

The storage capacity of the rain gardens will result in reduced peak flows reaching the local sewer, as water will be slowed and contained in the gardens.

Maintenance baseflow:

Information on Maintenance baseflow:

Possible increases to infiltration to groundwater from rain gardens, providing groundwater recharge and baseflows to the brook. However the influence is likely to be minor.

Water quality overall improvements:

N/A info

Information on Water quality overall improvements:

Rain gardens are designed to always intercept and treat the, often more polluted, first flush of highway runoff, ensuring this polluted water does not reach the Day Brook or the local sewer. However there is no available data for the quality of water flowing into or within the rain gardens.

Soil quality overall soil improvements:

N/A info

Lessons, risks, implications...

Key lessons:

The purpose of this pilot study was to prove that a retrofit design would work within an existing constrained urban area and will be accepted by both residents and experts. The specific design of these rain gardens and the site layout is shown to work, and could be replicated. Key lessons identified are that : - The measure provides proven surface water capture and infiltration, leading to reduced pressure on the local sewer and watercourse. - Active residents/ stakeholder engagement and involvement during design and construction helps ensure that concerns are being considered and that the scheme will be accepted and valued. - When delivered as a collaborative project, multiple benefits can be achieved such as knowledge transfer and local involvement and understanding. - It is important that all involved (from designers to the construction crew on the ground) are clear on what is to be achieved and how, before implementation/ construction begins.

Financing difficulties:

Success factor(s):

Type	Role	Comments
Successful coordination between authorities	main factor	The partnership approach between all stakeholders was critical to the delivery of the retrofit scheme and was very effective.
Communication activities	secondary factor	The positive attitude of the local residents and their involvement in meetings as the project progressed ensured support.
Other	secondary factor	The land was already owned by the local authority so there were no land ownership issues.

Financing:

Type	Comments
National funds	Environment Agency

Barrier:

Type	Role	Comments
Limited staff and consultant knowledge	main barrier	There was initial difficulty in getting the Council to accept a different and new approach. However once the approach was clearly explained, the council were fully supportive.
Lacking financing sources	secondary barrier	There was limited time and budget for design and construction of the scheme
Limited staff and consultant knowledge	secondary barrier	The implementation/construction of the gardens was more of a challenge than anticipated, due to lack of experience of contractors.

Driver:

Type	Role	Comments
Past flooding events	secondary driver	Previous rainfall events had led to property flooding downstream.
Availability of subsidies	main driver	Money available as part of wider Urban Diffuse Programme in the region

Socio-economic

Direct benefits information:

The use of rain gardens in a predominantly urban landscape provides a cost effective and adaptable means to reduce flood risk, while providing aesthetic value to highly populated area.

Costs land acquisition information:

No land aquisition required, as owned bythe council

Costs operation maintenance:

There are maintenance costs accociated with the scheme, but anticipated to be less than the original maintenance costs of the grass verges

Costs operational information:

Not quantified

Costs maintenance information:

Maintenance is now undertaken by Nottingham City Council. NWRM measures were designed to be minimal maintenance. To ensure fully operational inlets will occasionally need to be cleared and vegetaion maintained.

Costs disposal decommissioning information:

No information provided

Ecosystem improved biodiversity:

Ecosystem provisioning services:

Information on Ecosystem provisioning services:

Unlikely to be a signficant effect

Ecosystem water supply:

Ecosystem impact climate regulation:

Not relevant for the specific application

Information on Ecosystem flood control volume:

Reducing the volume of water reaching the Day Brook in rainfall events will reduce flood risk to downstream homes and businesses. The reduction in flows reaching the sewer will reduce risk of localised sewer flooding.

Ecosystem flood control return periods:

n/a

Ecosystem erosion control:

Policy, general governance and design targets

Policy description:

Within the highly urbanised area of Nottingham City, a total of 972 properties fall within the Day Brook floodplain, with previous fluvial events leading to property flooding downstream. Ribblesdale Road is parallel to some of the upper reaches of Day Brook, a heavily modified watercourse that has poor water quality due in part to numerous sources of diffuse pollution from the extensive urban catchment. A pilot study was implemented that reduced the volume of surface water flowing to urban drainage systems from the existing highway setting, reducing the volume of surface water flowing to urban watercourses.

Part of wider plan:

Policy pressure:

Policy requirement directive:

Policy impact:

Policy wider plan:

Wider plan type	Wider plan focus	Name	Comments
			Other plans, such as catchment flood managment plan have been implimented since the NWRM was implimented.

Policy area:

Policy target:

Target purpose
Runoff control
Peak-flow reduction
Increase Water Storage

Design & implementations

Application scale:

Other

Installation date:

2013

Performance timescale:

Immediate

Area (ha):

0.55

Area specifications:

The catchment area of the rain gardens is 0.55 ha

Size:

148

Size unit:

Design capacity description:

The scheme was designed to manage surface water runoff from a 1:30 year event. Designed to capture runoff from 5500 m2 of highway

Basis of design:

The scheme was designed to manage surface water runoff from a 1:30 year event

Constraints:

The available space on the grass verges and budget available were key considerations in the selection of Rain Gardens over other schemes considered such as tree pits or permeable paving. Groundwork undertook a scoping/ feasibility study to consider the options but there is no available documented information. The original plan for this scheme was to collect runoff from a surface area of 7100 m2, however only 5500m2 was incorporated into the scheme due to restrictions from underground services and a number of mature trees clustered in one section of Ribblesdale Road. Proprietary water attenuation cells were key to the initial design as they provide significantly higher void space capacity than clean stone. However, budget contraints meant that use of proprietary cells was reduced and replaced by stone fill in a number of gardens.

Favourable preconditions:

The availability of the existing grass verge with occasional mature trees along the entire length of the road, allowed the effective implementation and operation of the rain gardens.

Design contractual arrangement:

Arrangement type	Role	Responsibility	Name	Comments
		No information available

Design consultation activity:

Activity stage	Name	Key issues	Comments
Design phase	Local residents involvment in design		Participation from local residents in the design and future management of the rain gardens.
Other	Follow up survey		Post implimentation survey

Design land use change:

Design authority:

Authority type	Role	Name	Comments
	Financing	Environment Agency	Financial; guidance and ongoing evaluation
Other	Determination of design details of the measure	Nottingham City Council	Construction; Design and ongoing maintenance
	Implementation	Groundwork Greater Nottingham	Design; Implementation and community liaison
National water authority	Other	Severn Trent Water	Post construction modelling

Last updated: 18 Jun 2015 | Top

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Rain gardens for the Day Brook, UK

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