Field studies have been developed to support the Edexcel GCE Geography
Extreme Weather module.
Extreme Weather in the Barcelona area
Floods are a common characteristic of Mediterranean water
cycles. In the Barcelona region, there have been major floods in 1962 (with
possibly 1 000 people dead), 1971, 1988 and 1994. Local flash flooding is
becoming increasingly important, especially in the rapidly growing coastal
plains north and south of the city. Diffuse inundation after storms with
intensities of 200 mm/day or more is also becoming common.
Flash flooding occurred in the Barcelona area
between 11 pm local time of the 9th of June and 11 pm local time of the 10th of
June 2000. The maximum rainfall was recorded over the Llobregat basin, on the
Montserrat Mountain, with 224 mm, more than 80% recorded in less than 6 hours.
The Vendrell area had a maximum of 134 mm falling in less than 3 hours. This led
to flooding of tributaries of the Llobregat River and wadis that are normally
dry.
The estimated damage was more than 65 million euros and 5 people were killed.
However, this has not been the most catastrophic flood event recorded in the
lower part of the Llobregat basin. On September 20, 1971, 308 mm were recorded
in 24 hrs, with 19 deaths and damage estimated at $100 million. On this
occasion, the peak flow of the Llobregat River in Martorell (Montserrat) was
3080 m³/s, more than twice the peak flow produced in the June 2000 event. On
September 25, 1962, 250 mm were recorded in 2 hours near the Llobregat basin
causing 441 deaths and 374 missing. The analysis of ancient archives since the
14th century shows that catastrophic floods have affected this area once or more
each century, mainly in autumn. However, during the 17th, 18th and 19th
centuries, some catastrophic floods were recorded in Spring.
Fieldwork covers extreme impacts, increasing risks and managing
extreme weather.
Extreme impacts
Fieldwork includes a study of flood impacts along the Torrent del Lluc in El
Vendrell, investigating features of the floodplain and the flood management
schemes.
Extreme Impacts
Flash flooding occurred in the Barcelona area on 10th June
2000. The maximum rainfall was recorded on the Montserrat Mountain, with 224 mm
recorded in less than 6 hours. The Vendrell area had a maximum of 134 mm falling
in less than 3 hours.
The intensity was such that a state of emergency was declared
in El Vendrell.
Vendrell lies at the confluence of two normally dry rieras
(intermittent streams), the Riera de la Bisbal and the Torrent del Lluc. The
confluence of these two rivers flows across a main road into the town.
The Riera de la Bisbal had benefited from canalisation through
the town, but the Torrent del Lluc remained as a natural channel, running at the
same level as the main road in several locations. Flooding from the Lluc
seriously affected dozens of homes and businesses in the town centre.
A number of river management schemes have since been
implemented along the Lluc to prevent a repetition of the disaster. These have
had unexpected consequences.
The study examines the social and economic impacts of the
floods, investigating and mapping features of the floodplain of the Torrent del
Lluc. The effectiveness of the management responses is evaluated.
Fieldwork investigates the flood risks associated with the Riera de Ribes.
Riera
de Ribes: flash flood hazard study
Travel time: 15 minutes
The Riera de Ribes is normally a dry
river and the investigation is based on a historic flood notch on a river cliff.
The river flood cross-section and gradient are measured. Discharge is
calculated using the hydraulic radius and Manning n formula.
The risk to recent housing and camp site developments on the river floodplain
downstream can be assessed together with the effectiveness of river management
schemes.
This study introduces the concepts of river efficiency and competence.
Other factors that affect the flood risk, such as increased urbanisation,
forest fires, changing agricultural land use, drainage density, drainage basin
shape, reforestation, etc. can be analysed with the aid of secondary data. more
Managing extreme weather
A study of the flood management schemes in El Vendrell enables an
evaluation of the success of the existing strategies and how these might be
developed or improved in the future.
Click on map rectangles to view river management examples
Scale: 1 cm = 100 metres
All fieldwork is supported with secondary data. These fieldwork studies take
a full day.
