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.