Transcript Slide 1

MODELING OF LAND BUILDING IN THE MISSISSIPPI DELTA:
A TEMPLATE FOR RECONSTRUCTION
Wonsuck Kim & Gary Parker, University of Illinois
As part of a much larger team led by C. Paola (NCED) and R. Twilley (CLEAR)
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THE ORIGINS OF OUR LAND-BUILDING TECHNOLOGY:
CAN HUMANS JUMP-START THE NATURAL DELTABUILDING PROCESSES OF RIVERS?
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THE NATURAL PROCESS OF DELTA LOBE CONSTRUCTION
AND SWITCHING
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Lobe gif from M. Wolinsky
DELTA MADE BY HUMANS:
TAILINGS BASIN OF AN IRON MINE, LABRADOR, CANADA
~ 2.4 km
Sediment disposal
rate: ~ 24 Mt/yr
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DELTA MADE BY HUMANS:
TAILINGS BASIN OF AN IRON MINE, MINNESOTA
~ 3 km
Sediment disposal
rate: 21 Mt/yr
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WE HAVE DEVELOPED AND VERIFIED NUMERICAL MODELS
THAT DESCRIBE THE OVERALL EVOLUTION OF THESE
DELTAS DECADES INTO THE FUTURE
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HOW MUCH SEDIMENT IS CURRENTLY AVAILABLE FOR
DELTA BUILDING IN THE MISSISSIPPI DELTA?
Input: ~ 208 Mt/yr
Atchafalaya River:
~ 84 Mt/yr
Lower Mississippi River:
~ 124 Mt/yr
Wax Lake Delta:
~ 34 Mt/yr
Suspended
sediment loads
Atchafalaya Delta:
~ 50 Mt/yr
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TEST OF CONCEPT: NUMERICAL MODEL OF EVOLUTION OF
THE WAX LAKE DELTA
Atchafalaya River
Mississippi River
Wax Lake Delta
The delta started to formed in 1973, when it received
increased flow from the Atchafalaya River.
Its growth has been monitored ever since.
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OUR MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST
Before start of
delta growth
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THE MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST
Yellow: 38 Mt/yr
White: 25 Mt/yr
(suspended load)
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THE MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST
Yellow: 38 Mt/yr
White: 25 Mt/yr
(suspended load)
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THE MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST
Yellow: 38 Mt/yr
White: 25 Mt/yr
(suspended load)
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THE MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST
Yellow: 38 Mt/yr
White: 25 Mt/yr
(suspended load)
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PREDICTIONS INTO THE FUTURE OF THE WAX LAKE DELTA
HIGH
HIGH
LOW
LOW
HIGH: Solid line, 38 Mt/yr; LOW dotted line: 25 Mt/yr (suspended load)
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MIGRATION OF THE MODEL FROM WAX LAKE TO THE
MISSISSIPPI RIVER BELOW NEW ORLEANS:
Two diversions: Barataria Bay and Breton Sound (CLEAR plan)
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POTENTIAL SEDIMENT FOR DELTA BUILDING:
45% OF 124 Mt/yr, OR 56 Mt/yr (~ 3 iron mines)
45% of floodwater and
sediment diverted.
Breton Sound:
28 Mt/yr delivered
11 Mt/yr captured
Barataria Bay:
28 Mt/yr delivered
11 Mt/yr captured
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SCENARIOS MODELED
100 year simulations from 2010
Base case:
Subsidence: 5 mm/yr; sea level rise: 2 mm/yr
Variant parameters
Subsidence: 1 mm/yr, 10 mm/yr
Sea level rise: 0 mm/yr, 4 mm/yr
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Image from M. Wolinsky
PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
Takes only about
0.1 years to build
these initial deltas
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE
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VARIATION: SEA-LEVEL RISE RATE = 0 mm/yr, SUBSIDENCE = 5 mm/yr
Solid line: variant case
Dotted line: base case
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VARIATION: SEA-LEVEL RISE RATE = 4 mm/yr, SUBSIDENCE = 5 mm/yr
Solid line: variant case
Dotted line: base case
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VARIATION: SEA-LEVEL RISE = 0 mm/yr, SUBSIDENCE = 1 mm/yr
Solid line: variant case
Dotted line: base case
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VARIATION: SEA LEVEL RISE = 2 mm/yr, SUBSIDENCE = 1 mm/yr
Solid line: variant case
Dotted line: base case
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VARIATION: SEA LEVEL RISE = 2 mm/yr, SUBSIDENCE = 10 mm/yr
Solid line: variant case
Dotted line: base case
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VARIATION: SEA-LEVEL RISE = 4 mm/yr, SUBSIDENCE = 10 mm/yr
Solid line: variant case
Dotted line: base case
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IN ORDER FOR THE DIVERSIONS TO BE SUCCESSFUL,
CONTROL STRUCTURES AND SHORT GUIDE CHANNELS,
NOT OVERFLOW POINTS, ARE NEEDED
• We need to get as much sand as possible into the new deltas.
• The present Caernarvon diversion, while helpful, delivers mostly mud.
• We know how to build the control structures that divert sand as well as
mud, because we built the Old River Control Structure to regulate flow
into the Atchafalaya River.
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SLURRY PIPELINES CAN BE HELPFUL TO START LANDBUILDING
http://www.lacpra.org/index.cfm?catid=0&elid=0&fmid=0&md=pag
ebuilder&nid=31&pid=20&pnid=24&tmp=home
IF SUSTAINED FOR MORE THAN A FEW YEARS, HOWEVER, THEY CAN
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BUILD DELTA SLOPES THAT ARE TOO STEEP.
NEXT STEP: BUILD IN THE FINE STRUCTURE
• The land-building model predicts overall topography.
• We are using field measurements to build in the statistical structure of
bars/channels/edge effects/ etc. necessary for ecosystem modeling.
(m)
Many species of fish like this edge zone near bars.
-0.3 - 0
0.3
0.6
0.9
1.2
1.5
Our field effort on the Wax Lake Delta is our main template.
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NEXT STEP:
BUILD IN THE ECOLOGICAL
COMPONENTS OF THE NEW DELTA
Most of these components are already in place at
Louisiana State University and within the CLEAR group in
Louisiana.
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NEXT STEPS:
CONSIDERATIONS OF SUCH FACTORS AS
• Effect of diversions on Mississippi River upstream
• Coastal sediment supply
• Storm surge
• Navigation
• Socioeconomic implications: e.g. oyster farms, shrimp
• POLITICAL WILL
AMBITIOUS PROJECTS ARE POSSIBLE!
Parker’s great-grandfather and great uncle were construction workers on this39
first bridge to span the Mississippi River in New Orleans
Most of the Mississippi Delta, some 10,000 square miles, lies less than
three feet above sea level. Beset by land subsidence and rising sea levels,
much of this vast area will inexorably sink beneath the waters by the end of
this century.
BRUCE BABBITT
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Most of the Mississippi Delta, some 10,000 square miles, lies less than
three feet above sea level. Beset by land subsidence and rising sea levels,
much of this vast area will inexorably sink beneath the waters by the end of
this century.
OUR REPLY
BRUCE BABBITT
Before major human intervention, the Mississippi Delta historically
maintained itself with river slopes on the order of 3 ft of drop per 30 miles
without sinking beneath the waters!
How? The surface is NOT a static “board” that will sink because of its low
slope – it is a DYNAMIC, self-maintaining surface that keeps itself from
drowning by adding sediment to balance subsidence.
Think about your bank account.
If you withdraw $1,000 a month every month, you will go broke before long.
How can you fix the problem?
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Most of the Mississippi Delta, some 10,000 square miles, lies less than
three feet above sea level. Beset by land subsidence and rising sea levels,
much of this vast area will inexorably sink beneath the waters by the end of
this century.
OUR REPLY
BRUCE BABBITT
START DEPOSITING $1000 A MONTH!
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WE THINK THAT THE SCIENCE AND TECHNOLOGY EXISTS
TODAY TO REBUILD A NEW, LIVING MISSISSIPPI DELTA
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Wax Lake gif from M. Wolinsky