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In
years of heavy rains, Ventura County as well as other neighboring southern
California communities, experience additional water hazards due to swollen
water channels, flooded homes, overflowing rivers, flash floods, an increase
in traffic accidents and problems caused by mud slides. Often times SAR
personnel are asked to help offset the increase in emergency calls that the
county handles. Swiftwater rescue response has been defined as standard
protocol for the mountain teams within
Ventura
county. In severe cases of flooding, a local state of Emergency (possibly
expanding to State and
Federal
States
of Emergencies) may be declared.
Water
rescues are uncommon but their occurrence is devastating if a person,
especially a child, is swept into rapid moving water. SAR personnel are
trained in roped rescue systems that can be used to extract someone from a
waterway. Some basic systems are used and practiced by SAR personnel so that
they may be deployed quickly, efficiently, safely, and successfully. The
tyrolean itself plays an important role in water evacuations. In addition to
persons trapped in waterways (natural or otherwise) water rescues could
include vehicles trapped attempting to cross waterways, people stuck on a high
points of a waterway, missing persons in slow or still moving flood water,
trapped individuals in homes succumbed to flood waters or mud, as well as
evacuations of communities cut off by flood waters.
Although
it is not possible to predict when a water rescue will be required, moving
water always seems to create an attractive nuisance even in the worst weather
conditions. The presence of flooding water channels coincident with the
release of children from school or during a day when school is not in session
greatly enhances the chance that a rescue may be needed.
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Understanding
the Waterway:
Flood
zones typically follow prior burn areas but are not limited to these
areas. Some of the county areas near the foothills in Ojai, Piru,
Santa Paula
, and Fillmore serve as large collection tributaries which can easily flood
during high rain activity.
One
important element of swiftwater rescue is the ability to "Read the
Waterway." Reading the
waterway is the ability to note potential hazard zones and zones that may
be helpful rest zones or the best access and rescue zones.
Four
conditions are noted when rating the difficulty of a waterway:
the elevation loss (applicable in the foothills), the volume of
water, the geomorphic makeup of the waterway, and the number of local
hazards.
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Current Differentials:
Variations in the coarse of moving water.
Elevation
loss is intrinsically obvious but very hard to measure or gauge. The speed
and average depth of the water are more applicable to rescue work. Water
will flow fastest in the middle of a water channel where the depth is the
deepest. An offset channel will force the faster water to travel toward on
side or the other which is typically seen in waterway turns where often
the waterway narrows and the intensity increases. A cross section of a
waterway is shown in figure 1. Laminar flow is the majority of the
water flow which follows the path of the waterway. Helical waterflow is
waterflow that travels along the waterway in a recirculating pattern of
continuous eddy currents.
These
are also depicted in figure 1.
The
waterway should be considered cold enough to generate hypothermia.
Rescuers working near or partially in water (especially during a rain
storm) must be very aware of hypothermia conditions).
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