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Isar to Virgin RiverHuman Populations and River Ecology
Human Populations
Human populations have
always liked to live on river
banks for as long as we have
had cities.
How do we maintain river
systems while protecting our
populations? This is a problem
that has persisted for as just
as long as cities.
In Europe this has been dealt
with in a fairly traditional
way.
Isar River in München Germany, early wood print and
Roman wood carving showing est. of München
Isar River
• The Isar River is one of the most important tributaries of the Donau (Danube) River in Europe.
Isar River
• It stretches through many towns and continues on to connect to the Donau which eventually continues to the Schwarzes Meer (Black Sea).
Isar River
The Cities have grown right up
to the rivers edge through the
length of the river. So for
safety the river has been
changed along the length of
the river.
Isar river 2004 by Denniey Snyder
Isar River by Grzegorz Jereczek
Isar River
• Damage from WWII is still being repaired through Germany as can be seen in these pictures from the cathedral in Ulm and in the churches in München.
Isar
• Due to lack of time and resources following the war many rivers, including Isar, were simply cemented off into artificial "canal” like systems.
River Isar in Munich near
Deutsches Museum pre 2000 via
enacademics
Virgin River
• In the USA many systems similar to their counterparts in Europe are beginning to experience similar growing pains to those experienced 100-200 years ago.
Virgin River Watershed via Shannon wikicommons
How do we protect the
people while allowing them
to live near the rivers?
Virgin River
• In 2005 the Virgin River experienced a flood that caused severe damage to the area.
Virgin River
Virgin River
Virgin River
• What caused this devastation?− City allowed builders to build in alluvial basin
of the river.
Virgin River
− The system was over run with Tamarisk trees, which are not native but grow very fast, and Cotton Woods. The trees slow the flow of water which causes it to back up and flood.
Virgin River
• Following the Flood little was left in some areas to rebuild with.
RESTORATION VS PROTECTIONHow to Rebuild
Isar and Virgin
Isar River Virgin River
Length 183 miles (295 km) 162 miles (261 km)
Average Discharge 175 m³/sec Highly variable
278 m³/sec during flood
Elevation change 848 m 780 m
Population ≈200,000 ≈165000
Restoration Started 2001 2005
Est. Cost 28 million €
($30.5 million)
$56.8 million* (52.2
million €)
I have been to
Time to complete ≈15 years ≈3 years
Entire river? Yes Only St. George region
*Included damages done to house and properties of at least $35 million
Goals
• Isar− Restore native species− Restore leisure sites− Improve water quality− Restore banks by
removing canal system where possible
− Restore islands in stream and breath
− Improve flood control− Where possible restore
river path
• Virgin− Find a balance between
natural and designed river
− Straighten meandering river within city limits
− Lower river for floodplain evaluation
− Improve bank structure to increase stability
− Vegetate with native species
− Over widen river− Remove any debris or
exotics plants within river− Implement appropriate
bioengineering practices
Site Purpose: Isar
Hydroelectric, and Water treatment
Site Purpose: Isar
Restore Pre-World War I beaches
Site Purpose: Isar
Traditional sports and river recreation
Site Purpose: Isar
Modern recreation: Surfing, Kayaking
Site Purpose: Isar
Restore more native ecology
Site Purpose: Virgin
Make safer for people
Site Purpose: Virgin
Bring in plant
species that aren’t
exotics or as
damaging to the
native system
Site Purpose: Virgin
Improve quality of river for endangered species
Construction
In some areas the Virgin
River was completely
plowed to remove any
debris or exotics. This
way new soil and
structure could be laid
out.
Isar time was taken to set
up artificial dyke system
while river continued to
flow during construction.© imagebroker
Final design goals
Isar implements a restoration of a
gradual bank with a dyke that
drains with high water infiltration
rates positioned back behind the
bank itself.
Virgin lengthens the river and
places geotextile fabric with stones
to stabilize the bank and prevent
plants from growing down into the
river where they could slow the
flow.
FINAL ANALYSISIn Summary
How do these sum up?
• Isar is a true attempt to be a “river that reflects its alpine origin.” Within the city it is a “nature-oriented river landscape… that presents the metropolitan population a nature that is intact and attractive… and also provides a habitat for indigenous river plants and animals.”
• Virgin is “enhance stability, increase habitat, and enhance recreation (and) aesthetics.” In addition “removal of salt cedar and other exotic vegetation” while improving native species patterns.
Virgin Restoration?
• Virgin restoration secured the safety of the people but moved the river system to a design that is like that of the river systems of the late 1800’s and early 1900’s in Europe; a canal like safety system.
• Can it be called restoration?− Restored a structure of terraced systems on the
bank− Restored housing complexes− Was extremely successful at removing tamarisk − Improved river flow by removing all species in
stream
Focused on safety over ecology
Isar Restoration
• Restoration on Isar is still an ongoing process. It was hoped to be completed in 2015 but a flood that occurred in the construction zone in 2007 slowed the process. 80% of the restoration work is done but native species establishment is ongoing as a coalition of Universities across Bayern (Bavaria) continue to study old reports and raise species for transplants.− River quality- successful− River bank restoration- successful− Flood improvement- successful− Native species restoration- ongoing− Recreation improvements- successful
Isar River
References Arzet, K., & Joven , S. (2010). The Isar Experience –Urban River Restoration in Munich. München:
Wasserwirtschaftsamt. Binder, W. (2006). Case Studies: Isar; Germany. Munich: Bavarian Environment Agency. Natural Channel Design, Inc. (2007). Final Report Virgin River Master Plan. Flagstaff : Washington County
Water Conservancy District . Rivers by Design. (2011). Isar River Munich: Pamphlet. Munich: Munich River Alliance. Snyder, D. J. (2015, March 25). 2005 Flood. (M. D. Snyder, Interviewer) USGS. (2006). Flooding and streamflow in Utah during water year 2005. Washington D. C.: USDI.