Geoscience Reference
In-Depth Information
Acknowledgements
potential, for potable water and particularly for irrigation
water. In the UAE, apart from at a few desert oases, what
agriculture there is relates to irrigation from springs at the
toes of alluvial fans. In southeast Spain large-scale irriga-
tion from groundwater resources within alluvial fans sup-
ports modern agriculture that has been developed largely
on alluvial fan surfaces, agriculture that produces a wide
range of crops, including citrus fruit, salad crops, melons
and peppers. In the long term, whether this agriculture is
sustainable is open to question. Water does have to be im-
ported from outside the region and there have been recent
developments in desalination to combat local groundwater
shortages.
Groundwater occurrence within alluvial fans is not
necessarily simple. The finer horizons, debris flows and
palaeosols, act as partial aquicludes and groundwater flow
tends to follow buried channel systems. Reconstructing
the three-dimensional geometry is important for mod-
elling groundwater potential of alluvial fans (Weissmann
et al
., 2004). The reservoir potential of bodies of allu-
vial fan sediments for oil and gas has long been recog-
nised. Clearly, increased understanding of the hydrology
of alluvial fan sediments has potential in exploration for
hydrocarbons.
Dry-region alluvial fans therefore have importance for
settlement, land use and or their water resource poten-
tial. They are, however, hazardous environments, prone to
flash floods and related sediment problems. It is significant
that many of the documented flash flood disasters in the
USA have involved settlement on alluvial fans. Similarly,
in Alpine Europe, though not in any sense a dry region,
there have been a number of flood disasters on alluvial
fans. In planning the safe development of such zones, it
is important to understand the flash-flood risk. Modelling
the flash-flood hazard (Zarn and Davies, 1994) should
take account of the geomorphology of alluvial fans. For
example, such models should take into account the like-
lihood of channel switching to the flanks of a fan rather
than assuming that the zone of greatest risk is 'straight
down the middle'.
Dry-region alluvial fans are important features in their
own right. Understanding their processes and morphol-
ogy is fundamental to understanding the function of
fluvial systems in dry-region mountain environments.
They are also of considerable importance in unravelling
Quaternary environmental change in dry regions. Under-
standing their sedimentary processes has implications for
understanding alluvial fan sediment sequences in the an-
cient rock record. Finally, alluvial fan science has its
place in the safe and sustainable use of the world's arid
lands.
The author thanks the cartographics section of the De-
partment of Geography, University of Liverpool, and es-
pecially Sandra Mather, for producing the illustrations.
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