Lesson Plan
By: Claire Stewart
Topic: Hydrology / Geology – What it is?
Location of Teaching: On rocks at Elbow Rapid (if time allows it)
Time Required: ~20min (can be an on going lesson throughout the trip
Learning Focus
This lesson has been design to provide students with a broad understanding
regarding what hydrology means and to be specific, Big River hydrology.
Students at the end of the trip should be able to link this new knowledge with
information they have been taught in class to help them develop a solid
understanding of this river system.
Aims / Objectives
1. To study the Big River environment by using different field observation
methods and techniques. In particular to record details of unique geological and
hydrological processes of both the Big River and lake Eildon Environment.
2. To facilitate the students with the opportunity to develop a new connection
3. Students to develop a basic appreciation for whitewater and flat-water
paddling,
Content
What rock type is Big River?
Generally speaking, Big River is mostly metamorphic rock.
Metamorphic Rocks are the result of a transformation of an existing rock type, such as
Sedimentary or Igneous which have metamorphism (changed form). So how do
Sedimentary / Igneous rocks change? These rocks are under an enormous amount of
pressure which fosters heat build up, which therefore causes them to change. Strain and
fluids can also influence the transformation.
What is Hydrology?
Hydrology is the science of dealing with the way water moves through an area, of looking at
other areas including the properties, laws and geographical distribution. According to
Rescue 3 International there are four main factors which should be considered when
assessing the difficulty of any river.
These include:
a) Elevation Drop.
b) Volume of Water.
c) Geomorphic make up of that river.
d) Hazards and constructions.
Elevation drop can play a large roll in type of hydrology present in any river. This can
normally be shown in vertical meters in the particular section of river. Caution needs to be
taken in terms of general averages that can be misleading since some rivers concentrate
their elevation drop in only one section, therefore, hiding harder sections either before or
after the reading. Rivers like this are referred to as Pool and Drop rivers, for example Big
River. On the other hand there are other rivers that have a steadier elevation loss, which
can be more dangerous as there may not be any calm areas to recover and relax in, for
example the gorge section of the Mitta Mitta River
The volume of water is considered in conjunction with the elevation loss when determining
the difficulty of any river. The flow is measured in cubic meters per second, this being the
amount of water to pass by a particular point on the river bank at any given second. A big
river a large volume of water with a low rate of elevation loss where as a smaller river such
as Big River will have a large elevation drop but with significantly less water flow. The big
white water rivers have both, a high volume of water and a large elevation drop, but these
are not common in Australia, however do occur in sections of the Tully and North Johnstone
Rivers.
The make up of a river bed (geomorphic make up) itself determines significantly what type
conditions would occur in different sections on any river. This includes the presence or
absence of undercut rocks, pot holes and rock shelves. A river is said to be ‘technical’ if
there is a large presence of these features. In addition to the river bed the river bank can
also play a roll in how difficult a section may be. A steep gorge is much more serious than
an open undulating country.
Finally, a white water hazard is any obstruction or condition that is able to harm a paddler. A
hard object, such as a rock or a water feature such as a hydraulic is said to be a hazard. In
addition to these, trees and over hanging branches can act as snags and often post serious
hazards to novice paddlers. Temperature of the water and surrounding wildlife can also be
classified as hazards to inexperienced paddlers. Therefore there are a lot of considerations
that must be taken into account when paddling these kinds of rivers to safely avoid these
hazards.
Hydrology of Big River
Generally Big River is generalized to have a solid and constant Grade 2 white water, with
the occasional rock garden, that can be classified as Grade 3 in high water. Examples of
rapids that can vary between Grade 2 and 3 are Slalom, Elbow and a variety of rock
shelves, (Sean’s Fault) can also produce some nasty stoppers. In high water another
challenge is dealing with the constant fast chute of turbulent water that can flow throughout
the whole river. Generally Big River offers a range of different types and styles of rapids and
paddlers need to ensure they correctly navigate their way down. The river offers an
assortment of wave chains, hydraulics, strainers, turbulent water and other obstacles in their
path.
Between the Pines camping area and Sean’s Fault the river becomes quite narrow in
sections and as a result of this there are numerous rapids closely spaced at a Grade 2 level
with most of the rapids are situated in extremely rocky gardens. In this section the notorious
rapid known as Elbow, is only one kilometer from the last major pull out point known as
Dudley’s Flat. Elbow is generally more exposed in early winter creating a sudden drop
before entering into the ‘mini canyon’ of surrounding rocks. In low water Elbows is a solid
Grade 2+ rapid. The rest of the white water section is similar to the sections already
paddled, with a variety of different Grade 2 rapids. From there on in the river takes on a new
mood as it weaves its way across the floodplain to empty into Lake Eildon.