13/03/2006 - The Environment
Agency Flood Risk Management Team recently
completed a project to reduce flood risk
for the residents of Ferry Green, in the
village of Willington, South Derbyshire.
During the November 2000 floods, Ferry Green
residents experienced flooding from the
River Trent, combined with surface water
flooding from the road drains in the village.
We held a meeting with the local MP about
the flooding from the River Trent and agreed
to investigate the possibility of reducing
this flood risk.
We carried out a site investigation and
survey in the affected area of Willington
- mainly the public open space to the rear
of Ferry Green and Coach Way. The site investigation
and consultation with the residents identified
the following problems:
On the western side of the bridleway behind
the properties along Ferry Green a ditch,
which runs all the way along the side of
the Bridleway down to the River Trent, was
blocked and silted up almost to ground level.
A Severn Trent Water surface water sewer
pipe running from Hall Lane and diagonally
across the Bridleway, has a manhole in the
side of the ditch behind 4 Ferry Green,
which leads to an outfall pipe into the
River Trent.
The outfall pipe and headwall structure
had been washed away by the river and the
remainder of the pipe was completely blocked.
This caused surface water to discharge from
the manhole lid on the side of the ditch.
The water flowed backwards towards Hall
Lane due to the ground contours. This increased
flooding to the rear of the properties along
Ferry Green.
Our computer model shows that the properties
along Ferry Green did not have 1 in 100
year standard of protection from River Trent
flooding (i.e. a flood with a 1% chance
of happening in any one year). De-silting
the brook along the Bridleway to the River
Trent would encourage flood water to back
up the ditch and further increase the flood
risk to the properties along Ferry Green.
The solution was to build a small flood-bank
across the bridleway upstream of the manhole
and across the ditch. A new structure consisting
of a flap valve and penstock was constructed
in the ditch to prevent river water from
backing up the ditch and flooding the properties.
The flap valve will allow the ditch to drain
surface water to the river and the penstock
is a safety back up valve should the flap
valve fail during times of river flooding.
The work has a minimal impact on the environment
due to the working methods chosen and a
section of the ditch was enlarged to create
a small habitat scrape to improve the environment
for wildlife.
The work took ten weeks to complete and
included the use of sustainable construction
techniques and materials to save on natural
resources.
More information
The completion of this work has reduced
the flood risk to the 100 year standard
for the properties in Ferry Green (i.e.
it protects from a flood with a 1% of happening
in any one year) and has removed the concerns
of the local MP regarding flood risk from
the River Trent in Willington Village Derbyshire.
Seven properties were protected from river
flooding. The improvements to the ditch
also reduced the risks from surface water
flooding. The project cost £60,000
Materials used:
105 Tonnes of clay – waste from coal seams
at Ashby de la Zouch
20 tonnes of sub-soil – re-used material
already on site
20 tonnes of top soil – re-used material
already on site
41 tonnes of aggregate – crushed recycled
concrete
21 tonnes dust aggregates – quarry aggregate
from grading process waste
9m3 concrete – using recycled aggregates
110 metres timber – post and rail fencing,
from sustainable softwood sources.
