Confluence, in geography, describes the meeting of two or more
bodies of water. It usually refers to the point where a tributary
joins a more major river, called the mainstem, when that major
river is also the highest order stream in the drainage basin.
The term is also used to describe the meeting of tidal or other
non-riverine bodies of water, such as two canals or a canal and a
lake.
Two such examples of confluences in the United States are:
• The merging of the Monongahela and Allegheny Rivers. This merging
point is the beginning of the Ohio River, thus forming a confluence
in Pittsburgh.
• The Madison, Jefferson and Gallatin Rivers in Three Forks,
Montana form the confluence of the Missouri River, one of the
longest rivers in the United States (2,341 miles (3,767 km))
In Utah you also have a confluence along the Virgin River, though
not as big as the two other US examples.
About the River:
The Virgin River is a nearly 160 mile (322 km) long tributary of
the Colorado River in the southwestern United States. It begins in
Southwestern Utah, at the Navajo Reservoir in the Dixie National
Forest, north of Zion National Park near Springdale, and is formed
by the confluence of the East Fork Virgin, that flows through Mount
Carmel Junction on the east side of Zion National Park and
Parunaweap Canyon, with the North Fork Virgin River, that flows
from Navajo Lake through Zion National Park. The river flows in a
southwesterly direction, passing south of the old townsite of St.
George where the Santa Clara River joins the Virgin at a place the
Paitues called Tonaquint. The river then flows across the
northwestern corner of Arizona through the Virgin River Gorge and
past the towns of Beaver Dam and Littlefield. It enters southern
Nevada near the town of Mesquite and empties into the Colorado at
the Lake Mead reservoir, approximately 40 miles (64 km) east of Las
Vegas. The last 30 miles (48 km) of the Virgin River forms the
north arm of Lake Mead.
The river is home to the Virgin spindace, Lepidomeda
mollispinus, a type of minnow, and the Virgin River desert sucker,
Catostomus clarkii utahensis.
Water in the river's lower valley provides irrigation for the
cultivation of cotton, pomegranates, and figs. In fact in the
canyons around St. George you will find the letter D and the word
Dixie in the hills, this was because of the cotton that was grown
in this region.
About Canyons and how they are formed:
Rivers are a powerful erosive force. Over time, they wear down even
the tallest mountains and carry away the physical evidence that the
mountains once stood. Powered by the force of gravity, the world's
rivers deliver about 20 billion tons of rock and soil to the oceans
each year. Depending on the coarseness and volume of sediments they
carry and the speed at which they move, rivers erode their channels
at different rates.
Erosive forces continue to shape the Canyons today, millions of
years after they began to form. Normal channel erosion alone,
however, cannot explain the many kilometers that separate its rims.
The strongest explanation holds that the major factor in the
widening of the canyon has been activity from tributary drainage
systems -- the side streams, rivulets, and gullies outside the main
river channel. The greatest erosive force in these tributaries is
the fast-moving landslide called a debris flow.
Debris flows result when flash flooding from intense rainfall or
rapid snowmelt moves loose rock and boulders down canyon walls and
side channels. Debris flows are particularly likely to occur in
desert conditions, where the hard-baked soil and scarcity of
deep-rooted vegetation do little to absorb water or hold rocks in
place during heavy rains. Piles of loose soil and rock that collect
in a channel are picked up by the water and carried quickly
downstream. The action of the debris tears away at the banks and
bed of the river, thus widening the surrounding canyon. The faster
the water moves the more debris it carries and the more erosive the
debris flow becomes. Debris flows, which may resemble a river of
concrete more than a river of water, can carry car-sized boulders
and travel a mile or more, depending on the terrain. When they
reach more level ground and the flow stops, thick deposits form
over a broad area. The size of the deposits downstream reflects the
extent to which erosion has occurred upstream.
Of 36 Colorado River tributaries, of which the Virgin River is
one, recently studied, all had characteristic debris-flow deposits.
Nearly 60 percent showed evidence of debris-flow activity during
the last 25 years. Composed of 10 to 40 percent sand by weight,
debris flows in the Grand Canyon transport much of the sediment
that builds beaches along the river. Large boulders transported by
debris flows may also create or change its rapids.
To claim this cache you will need to park at N 37 11.760 W 113
17.332 and obtain some information at that site. There is a marker
here that provides some history of the discovery of this
region.
From the parking area you will need to proceed NW until you see
an old camper shell, to the left of the camper shell there is a
break in the fence that you can go thru and then follow your
GPS.
Please use caution as there is an unfinished basement nearby and
you will be on the edge of a canyon. From this spot you should be
able to see the confluence of the Virgin River and one other river,
however please use caution.
To claim this cache I am asking for the following
From the parking area:
1) What is the site number on the marker?
2) What are the names of the two other rivers besides the
Virgin?
3) If you step past the marker there is a Capital Letter in white
in the nearby hills, what letter do you see?
From the confluence:
4) I forgot my camera in my car when doing a nearby cache (GC16YZC)
so please take a picture of the confluence either showing your GPS
or a team member with the GPS.
5) The Virgin River will be the river nearest the canyon you are
standing on, what is the degree of the angle the second river
entering into the Virgin River? Please note I understand this
requirement will have to be your best guess
Please email me the answers to numbers 1, 2, 3 & 5, do not
put them in your logs. Post the picture with the log. If you do not
complete all five steps your log will be deleted
