25/04/2005 - The Environment
Agency took to the skies this week as part
of its drive to reduce the risk of flooding
in Oxford.
On Monday 18 April, a light aircraft equipped
with sophisticated LIDAR (light detection
and ranging) survey equipment mapped the terrain
across the Oxford floodplain.
LIDAR uses radar technology to take precise
ground level readings. Measurements across
a total surface area of approximately 60 square
kilometres were recorded, from Kennington
in the south to Yarnton in the north, and
from New Marston in the east to North Hinksey
in the west.
The information gathered will be used to
enhance the Environment Agency’s understanding
of floodwater movements during a flood event.
It will also play a critical role in assessing
the effectiveness of each of the potential
options for managing flood risk in Oxford
currently being examined by the Environment
Agency.
These are all based on two ‘core’ solutions
that could be implemented either as stand-alone
schemes, in conjunction with each other, or
with additional measures.
The two core solutions are:
widening existing streams to maximise the
volume of water they can convey
creating a new channel that will substantially
increase the volume of water that can be carried
through Oxford.
The additional measures that could also be
incorporated as part of an integrated solution
are:
storing flood water in reservoirs upstream
of Oxford for controlled release back into
the Thames and Cherwell rivers when their
flows return to normal levels
changing the use of land upstream of Oxford
- for example, planting substantial numbers
of trees on pasture to create woodland areas.
This would slow the passage of water downstream.
The survey aircraft, a twin-propeller Cessna
404, was positioned and navigated using satellite
global positioning (GPS). It flew 24 passes
over the Oxford floodplain at a height of
800 meters and every metre along its flightpath
a laser swept the ground to a width of 600
meters to take surface readings.
“We are looking to substantially reduce the
risk of flooding to a large part of Oxford,”
said Rob Hall, project manager for the Environment
Agency. “The area in question includes numerous
schools, two hospitals and the rail link to
London as well as thousands of residential
and commercial properties. A serious flood
would have a major impact, and this is what
we are working to avoid.
“Employing advanced techniques such as LIDAR
surveying will not only enable us to identify
the most effective options from our shortlist,
but also present the strongest possible case
for funding to Government.”
