Environmental Engineering Reference
In-Depth Information
23
Flood Modelling in the
Thames Estuary
JON WICKS, LUKE LOVELL AND OWEN TARRANT
Introduction
flood forecasting, warning and other operational
uses.
.
Broad-scale 2D inundation modelling for use in
appraising strategic flood risk management op-
tions (for the TE2100 project).
The chapter concludes with a discussion, based
on the experiences of modelling the Thames Es-
tuary, of where current modelling practice meets
the current needs and where further advances are
required.
Flood modelling is now an essential tool in the
analysis of many of the components of flood risk
management introduced in previous chapters.
However, it is not always easy to decide on the
most appropriate flood modelling method for spe-
cific tasks. This chapter uses case studies from
the Thames Estuary to illustrate which flood
modelling methods have been found to be most
appropriate for a range of flood risk management
analysis needs.
The chapter starts by providing background on
the Thames Estuary and London covering histor-
ical flooding, flooding mechanisms, current flood
risk management measures and a short history
of Thames Estuary modelling. There then follow
sections that describe how four flood risk man-
agement needs have been addressed using differ-
ent types of modelling:
.
One-dimensional (1D) hydrodynamicmodelling
of the main channel to generate extreme water
level values for assessing defence levels and pro-
viding boundary values for use in local breach
analysis (e.g. for flood risk assessments).
.
Detailed 2D inundation modelling of the flood-
plain to produce flood maps for development con-
trol, awareness raising and other uses.
.
Linked real-time 1D hydrodynamic modelling
with local detailed 2D inundation modelling for
Flooding and the Thames Estuary
Flood history on the Thames estuary
As a result of sea level rise, loss of marshland and
general encroachment, the tidal limit of the
Thames has slowly migrated upriver over the
centuries. The high water level through central
London has steadily increased, along with the
potential for higher extreme water levels (Gilbert
andHorner 1984).Notablefloods occurred in1099,
1236, 1663, 1791 and, more recently, in 1928,
when 14 people were drowned. Most recently, a
tidal storm surge in 1953 exceeded the 1928 level
at London Bridge by 23 cm. Considerable damage
and flooding occurred along the entire east coast of
England and in total 300 people were drowned,
many of them residents of Canvey Island on the
Thames Estuary. Until this event, the 1928 level
was the highest on record.
In 1965 a surge tide almost as high as that
recorded in 1953 entered the Thames Estuary.
Fortunately, this time there was little flooding as
