Flood Bypasses
As A Floodplain Management
Technology
University of California Washington – 27 January 2012
G. Mathias Kondolf
University of California, Berkeley, and Clarke Scholar, Institute of Water Resources, USACE
Anna Serra Llobet
University of California, Berkeley
Purpose, goals of workshop
• Propose a typology of flood bypasses
- advantages/disadvantages
- ecological benefits, land requirements
• Review performance of flood bypasses on the
- Mississippi River (2011)
- Sacramento River
• Consider when most effective,
limitations/barriers to implementation
• Develop guidelines for flood bypasses
Agenda
9.00
Flood bypasses: what do we mean?
Flood bypasses: examples in China, EU & US
Matt Kondolf and Anna Serra Llobet
9.15 Bypassing floods on the Sacramento: history and future prospects
Katie Jagt , American Rivers
Discussion
10.00 Ecological functions of flood bypasses
Todd Strole, TNC St Louis
10.45 Break
10.45 Bypasses in the 2011 Mississippi Valley floods: Lessons learned
Scott Whitney, Mississippi Valley Division
Discussion
Agenda
11.30 Panel 1. What made the Sacramento/Mississippi bypasses
effective? What are limitations/barriers to bypasses in
current policy?
Scott Whitney; Shana Udvardy, American Rivers; Pete
Rabbon, USACE HQ, (Moderator: Scott Nicholson)
12.00 Lunch
13.00 Panel 2. Can we develop guidelines for when are flood
bypasses applicable?
Panel: Sam Riley Medlock, ASFM; Todd Strole; Paul Wagner
IWR; Katie Jagt , American Rivers (Moderator: Matt Kondolf)
Agenda
14.00 Small groups break out to develop guidelines, identify topics
for Berkeley graduate student research
15.00 Reconvene, report
15.30 Adjourn
Flood Bypasses
What do we mean?
G. Mathias Kondolf
University of California, Berkeley, and Clarke Scholar,
Institute of Water Resources, USACE
Anna Serra Llobet
University of California, Berkeley
Definitions – disappointing?
• “A flood bypass, referred to as a floodway, is created by
diversion works and topography that permits excessive
amount of water in a river or stream to be directed into a
depression that will convey the flood water across land which
can tolerate flooding.” (Masoudian, 2009)
Commentary: Definition assumes bypasses must be on low-lying land,
would not encompass engineered channels. ‘Floodway’ is typically
used in broader sense. Need a better definition.
SOURCES: Mohsen Masoudian (2009). The topographical impact on effectiveness of flood protection measures.
Kassel university press GmbH, Kassel.
Definition
• “The defining characteristic of a bypass is
that it routes waters around a constrained
reach where consequences of flooding are
particularly undesirable” (John Cain)
Among key variables to consider:
• Frequency and duration of inundation (dry in non-flood?)
• Potential ecological functions
• Land use and land costs
• Mechanisms for purchase or easement
Room for the River (The Netherlands)
• The Netherlands
Population: 16,783,092
Land below sea level: 25% + 25% more subject to flooding
• Room for the River
Reason
The water in the rivers reached
extremely high levels in 1993
and 1995. 250,000 people had
to be evacuated in 1995
Budget
€ 2.3 billion
Planning
Start: 2007
Completion: 2015
Current maximum discharge
capacity
15,000 m3/sec
Discharge capacity on completion
16,000 m3/sec
Improve the environmental quality
of river areas
“Living With Water” will promote
communities that value and adapt to
water instead of fearing it
Room for the River (The Netherlands)
Objective
Room for the River will reduce
high water levels in the Rhine,
Meuse, Waal and Ijssel Rivers.
By 2015, these rivers will be
given more room at 39
locations, using a variety of
strategies.
Room for the River (The Netherlands)
Lowering of floodplains
Deepening summer bed
Water storage
Dike relocation
Lowering groynes
High-water channel
Depoldering
Removing obstacles
Strengthening dikes
video
Only in areas in which
creating more room for
the river is not an option.
SOURCES: Room for the River Project
Flood Bypasses: What do we mean?
Levee setback/removed
Pulling levees inland makes the
flood plain wider. Some levees
can be removed completely to
allow once-reclaimed land to
flood.
Transitory water storage
or overflow basin
Some water can be
routed to lake beds for
temporary storage.
Flood bypass
A high-water channel is
designed to route
overflow away from the
river.
SOURCES: Room for the River Project / American Rivers. Alberto Cuadra and Bonnie Berkowitz / The Washington Post. Published on
May 8, 2011, 9:59 p.m.
Flood Bypass vs. Reconnected Floodplain
• Flood bypass (high water channel, flood overflow channel)
• Conveys flood waters
• Usually implication: separated from the channel
• Transitory storage
• On time scale of flood, water does not return to channel
• Reconnected floodplain
• Set back levees-floodplain conveyance adjacent to channel
Flood Bypasses: What do we mean?
Reservoir
Off channel
storage
Reconnected floodplain/polder
Flood bypass
Flood Bypass systems
Bypass tunnel
Engineered
Natural channel Floodplain
bypass channel
bypass channel bypass
Guadalupe River
(CA, US)
Waal River
Dijle River
(The Netherlands) (Belgium)
Yolo Bypass
(CA, US)
Residence time
Ecological benefit
Land requirements
Reconnected
floodplain
Sigma Project
(Belgium)
Flood Bypass systems
Bypass tunnel
Engineered
Natural channel Floodplain
bypass channel
bypass channel bypass
Guadalupe River
(CA, US)
Waal River
Yangtze River
(The Netherlands) (China)
Yolo Bypass
(CA, US)
Residence time
Ecological benefit
Land requirements
Reconnected
floodplain
Sigma Project
(Belgium)
Flood Bypasses:
some examples in China,
Europe and the US
Anna Serra Llobet
University of California, Berkeley
Flood Protection System, Yangtze River
Region: Downstream Three
Gorges Dam (China)
River: Yangtze River
Measures: Natural flood bypasses
leading to off channel floodplain
lakes
Summary: For centuries the
Chinese people have been
building earthen dykes and
diversion works to prevent floods
in the Yangtze River. Ironically, the
risk of a flood disaster has grown
dangerously high.
Three
Gorges Dam
‘Room for the River Waal’
Region: Nijmegen (The Netherlands)
River: Waal
Year: 2013-2016
Practical measures: levee setback
Summary:
The dike along the river Waal will
be replaced 350 meters land
inwards, leaving an island in the
middle of the river.
Source: www.floodresiliencity.eu
The Danube Island Project
Region: Vienna (Austria)
River: Danube
Year: 1972
Practical measures: flood bypass
channel
Summary: In 1972, an
approximately 21 km-long flood
bypass canal – the “New Danube”
was constructed to direct the water
during the floods and used the
excavated material to create a flood
free island –Danube Island –
between the new waterway and
the existing river bed.
Source: www.unhabitat.org
Sigma Plan
Region: East Flanders (Belgium)
River: Schelde
Year: 1997/2005
Practical measures: reconnected
floodplain - bypass channel
Summary:
The plan contains the following
trends:
- Heightening of the dikes
- to give water more space. The
creation of approximately 4000
hectare of free water space in case of
a flood.
Source: www.gogkbr.be/index.php?page=wat&hl=en_US
Yolo bypass
Region: Upstream Sacramento
Delta (California, US)
River: Sacramento
Year: 1933
Practical measures: Floodplain
bypass channel
Summary: During the winter
months, weirs in the levee
systems release water into the
floodway to avoid flooding
inhabited areas of the counties.
Yolo bypass
location
Guadalupe River Project
Region: San José (California, US)
River: Guadalupe
Year: 1997-2001
Practical measures: flood bypass
tunnel
Summary: A key outcome of the
project was to include a double
box bypass culvert to help convey
flood flows while avoiding and
maintaining critical riparian and
shaded riverine aquatic habitats.
Guadalupe River Project Collaborative
Key element: Underground bypass box culvert system
Plan view
Napa River bypass
Region: Napa (California, US)
River: Napa
Year: 2010-2015
Practical measures: flood bypass
channel
Summary: Project: The $400 million
Napa River/Napa Creek Flood Control
Project is lowering dikes, creating
floodplains and a bypass, relocating
bridges and restoring 900 acres of
wetlands according to “living river”
principles.
Flood control bypass channel
Overview
Flood control bypass channel
High tide
Flood control bypass channel
Flood
Source: www.napavalleyregister.com
Bird’s Point-New Madrid Floodway
Region: Missouri, US
River: Mississippi
Year: Mississippi River and
Tributaries Project, 1928
Practical measures: floodplain
bypass
Summary: Performed well in
the 2011 floods, protecting
Cairo, IL.
Bird’s Point-New Madrid Floodway
Morganza Spillway
Region: Louisiana, US
River: Mississippi
Year: 1930-1954
Practical measures: floodplain bypass
Summary: Its purpose is to divert
water from the Mississippi River
during major flood events and to help
prevent the Mississippi from changing
its present course through the major
cities of Baton Rouge and New
Orleans.
Bonnet Carré Spillway
Region: St. Charles Parish
(Louisiana, US)
River: Mississippi
Year: 1931
Practical measures: Floodplain
bypass (delta distributary)
Summary: Is a flood control
operation in the Lower Mississippi
Valley, which allows floodwaters
from the Mississippi River to flow
into Lake Pontchartrain and then
into the Gulf of Mexico.
Bypassing floods on the
Sacramento: history and future
prospects
Katie Jagt
American Rivers
Ecological functions of flood
bypasses
Todd Strole
TNC St Louis
Bypasses in the 2011
Mississippi Valley floods:
Lessons learned
Scott Whitney
Mississippi Valley Division
Panel 1.
What made the
Sacramento/Mississippi bypasses
effective?
What are limitations/barriers to
bypasses in current policy?
Moderator: Scott Nicholson
Scott Whitney; Shana Udvardy, American Rivers; Dave Wegner, Water & Power
Subcommittee, House T&I Committee; Pete Rabbon, USACE HQ
Panel 2.
Can we develop guidelines for when are
flood bypasses applicable?
• Taking a systems perspective, when is this technology applicable:
environmental context, socio-economic context, and at what scale in
the landscape?
• How can this technology support sustainable growth and resilience?
Moderator: Matt Kondolf
Sam Riley Medlock, ASFM; Todd Strole, TNC St Louis; Paul Wagner, IWR
Small groups break out to
develop guidelines, identify
topics for Berkeley graduate
student research
Reconvene, report
Next meeting
“Wise-Use of Floodplains:
Adaptation in America and Europe”
Workshop Fri-Sun 9-10 March 2012
University of California, Berkeley
Thank you!
G. Mathias Kondolf kondolf@berkeley.edu
Anna Serra Llobet
annaserrallobet@berkeley.edu