Environmental Engineering Reference
In-Depth Information
ever, a large proportion of the catchment suffers
from frequent and persistent flooding, which se-
verely constrains production and prevents realiza-
tion of the region's full economic potential. In
addition to their impact on the agricultural econ-
omy, floods also threaten numerous settlements
within the basin, disrupt road and rail communi-
cations and put vital infrastructure at risk.
The physical geography of the catchment is the
single most important factor affecting the way
that floods develop and impact the people, com-
modities and infrastructure. The landscape of the
entire catchment is dominated by ancient aeolian
features that have been modified by more recent
fluvial processes, reflecting the humid conditions
that have developed in what was once an arid
region (Fig. 22.2). In essence, relic dune fields
dominate the terrain of the Northwest area (Re-
gion A in Fig. 22.1), while the landscape of the
eastern and central parts of the catchment is char-
acterized by numerous lakes, wetlands and
marshes (Region B in Fig. 22.1). The basin's very
low slopes, coupled with the relative youth of its
surface water drainage system, means that rivers
draining the catchment have not yet had time to
adjust to the present, more humid climate, and
they lack both the drainage density and channel
conveyance capacity necessary to convey even
that is able adequately to represent flood processes
while also being capable of informing decision-
making by being sufficiently fast and flexible to
perform the multiple runs necessary to support an
integrated appraisal of a range of options for
intervention.
The practical utility of the concepts andmodel-
ling strategies presented herein is demonstrated
using examples and experience gained during the
development of a master plan for flood risk man-
agement in catchment of the R´o Salado, Argen-
tina (Halcrow Group 1999).
The R´o Salado Basin
The R´o Salado Basin covers an area greater than
170,000 km 2 in Buenos Aires Province, Argentina
(Fig. 22.1), and has a population of around 1.3
million. The catchment is one of the most impor-
tant lowlands inArgentina, with only 130mof rise
in elevation from the sea to the watershed 600 km
to the west. The generally low relief is interrupted
only by two ranges of Precambrian hills (ascending
to about 900m above sea level) in the far south of
the basin. The R´o Salado Basin plays a key role in
the nation's economy, contributing 25% of grain
and 30% of meat production respectively. How-
Fig. 22.1 (a) Location of Buenos
Aires Province within Argentina.
(b) Location of R´o Salado Basin
within Buenos Aires Province. A:
Northwest Region; B: Salado,
Vallimanca and Las Flores river
valleys; C: South-Western Lake
System. The red box shows the
location of a dune field area within
the Northwest Region (A). (See the
colour version of this figure in
Colour Plate section.)
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