Transcript River Crossing - Whitireia Moodle

River Crossing
Statistics
• Drowning is consistently the third highest
cause of unintentional death in New Zealand,
surpassed only by road vehicle crashes and
accidental falls.
• More people drown in rivers than in any other
aquatic environment in New Zealand.
2011 and 2014 River drowning stats
•
•
•
•
2014
2013
2012
2011
21 px
26 px
21 px
31 px
23%
24%
23%
24%
River deaths account for 1/3 of all NZ drownings
On average
• Average 3-4 deaths a year, 80% happen in flooded
rivers or side streams
• We don’t know how many near-miss river crossings
occur
• 7px died in Mangatepopo Canyon Tragedy 2008
• 2 trampers died in 2016 already this year!
Age group
•
•
•
•
15-24yrs
35-34yrs
45-54yrs
25-35yrs
1st
2nd
3rd
4th
Characteristics of rivers
Small Bush Streams
•Medium to fast current
•Water level can rise quickly
•Often boulders with slippery rocks
•Usually shallow
Steep Rivers
• Steep gradient causes fast flow
• Water level rise can be
very serious
• Narrow channels with steep
banks, often found in ravines/
gorges
• Steep, often continuous rapids
• Very difficult to cross
Braided Rivers
• Fast flowing
• Slow to rise at first, then can
rise very fast
• Rock and gravel river bed
• Shallow channels when not in
flood
• Many channels, channels can
be wide
• Riverbed is unpredictable
because it changes
Deep Sluggish Rivers
•Slow, no rapids
•River levels rise with flood, speed rises
• Mud/silt
•Deep
•Hard to cross due to depth and size
River Features
When water flows downstream it
prefers to travel in a straight line.
When it hits objects it is forced to
change direction, this forms water
features(rocks, bends, trees)
What feature is this?
Standing Wave
What feature is this?
Re-circulating Wave
Name the incident?
Rock Pin(ing)
Where are the Eddies?
What feature is this?
Strainer
What feature is this?
Sieve
Channels / Tongue / V’s
Current and River Flow
• Current , is where the main area of water
flows in a river
• The River flow is measured in Cumecs (cubic
meters squared per second)
• 1 Cumec = 1 Tonne= 1 Baby
River crossing decision making
• Do I need to cross?
• Where should I cross?
• How should I cross?
Considerations
• Depth: The greater the depth of water - more
pressure placed on people trying to cross it.
Once water reaches the height of your pack
you become buoyant
• Speed of current: if current speed faster than
walking pace (i.e. throw in a stick and walk
parallel with it from the bank), it is too fast to
cross safely.
• Rapids: white water caused by steep parts,
rocks or narrow parts of a river. Generally not
safe for river crossings.
• Waterfalls: where water flows over a drop in
the river. Often have powerful holes or rocks
at the bottom. River crossings should not be
performed upstream of water falls.
• Strainers: Trees or fences etc. Can trap a
person underwater
• Rocks: Can cause foot entrapment and push a
person forward or back. If this pressure is too
strong they will not be able to free
themselves. Can injure a person if they are
travelling with the current
Foot Entrapment
• Aerated Water: Generally formed by waterfalls,
holes and other features that mix air with the
water. Buoyancy is lower so staying afloat
becomes difficult. Not a suitable area for crossing
rivers.
• Undercut Banks: Have water flowing onto or
along them. An undercut is often indicated by the
lack of buffer or cushion wave. Very dangerous as
they can pin swimmers or boaters underneath
the water. To be avoided when crossing rivers.
• Overhanging Trees: Can trap swimmers.
Especially hazardous on river bends where the
current flows under them e.g. willow trees
• Bends: Water is at its greatest depth and
strongest flow on the outside of corners
• Alternatives: What are they
The place to cross
Where Do I cross?
There is no where to cross!
How to cross
Everyone here
Gives support
Types of Grip
Suggested method
Preferred method
One man method
Note – foot and pole
position
Current
Pole
Foot
Foot
Medical Conditions
• Hypothermia
– Body core temperature
falls below 35° (normal
body temp 37°)
– Mental deterioration
– Loss of physical ability
• Treatment
– Warm, dry, environment
– Warm gently esp torso
and head
– Give warm food and
drink only if victim is
fully alert.
Medical Considerations
• Cold shock (cold water immersion)
– Temporary immersion into cold water
– Over breathing response increases risk of inhaling
water
– Sudden drop in blood pressure, similar to fainting
– Loss of muscle coordination
– Cold skin insensitive to injury
• Treatment
– Same as Hypothermia