CHALLENGES IN
DELTAS UNDER
PRESSURE
James (Jai) Syvitski
&
S A Higgins
CSDMS
www.iahr2015.info
Facebook: IAHR2015
Twitter:
@IAHR2015
#IAHR2015NL
On Deltas and Humans
My Love of Deltas
Delta Blues
Syvitski 2015, IAHR
I was grew up on the Kam delta
It became my first (1975) thesis.
My ‘78 doctoral thesis was on
another delta.
Over my career I visited and
researched another 50 deltas.
I know and love deltas. They
are like snowflakes, similar yet
different.
Syvitski 2015, IAHR
Pristine deltas are dynamic wetlands,
with lobe & channel switching, and
shorelines shifting under the influence of
rivers, tides and waves.
They offer lush vegetation, diverse
forests, wildlife, fisheries, & rich organic
muddy soils. Movement through these
ultra-flat environments was mostly
aquatic.
Syvitski 2015, IAHR
Delta wetlands were also host to many
(sub) tropical infections, from diseasecarrying insects to parasites and wildlife
that kept human populations low.
Syvitski 2015, IAHR
Yearly Landsat images
Most deltas formed ~7000 y ago when sea level was stable. But human-causes
also contributed to the generation of modern deltas (e.g. Po, Ebro, Rhone,
Yellow). For example deforestation in Madagascar let to many new deltas
(MOVIE).
Syvitski 2015, IAHR
2
20th Century Transformation
Population & Migration
Engineered Water
Damn Dams - Missing Water & Sediment
Changes in Land Use
Syvitski 2015, IAHR
3.2 billion more people by 2100 1E+10 World Popula+on 9E+09 8E+09 7E+09 6E+09 5E+09 4E+09 More than 0.5 billion people live -­‐
3E+09 work on deltas, and their megaciFes. 2E+09 1E+09 0 1000 1200 1400 1600 1800 2000 City
Karachi
Kolkata
Dhaka
Rangoon
Bangkok
Ho Chi Minh
Hanoi
Guanzhou
Shanghai
Tianjin
Cairo
Buenos Aires
Delta
Indus
Ganga
Brahmaputra Irrawaddy
Chao Phraya
Mekong
Red
Pearl
Changjiang
Old Huanghe
Nile
Parana
1975
4.0
7.9
2.2
1.8
3.8
2.8
1.9
3.1
11.4
6.2
6.0
10.9
2000
10.0
13.1
9.5
4.4
7.4
6.6
7.8
8.9
12.9
9.2
10.5
11.8
2010
12.0
15.1
13.0
6.3
11.9
10.0
14.5
12.8
20.0
10.3
14.5
12.8
2200 Migra+on 12 delta ciFes have gone from 62 M people in 1975 to 153 M people in 2010 pink: 1813
red: 1831
brown: 1897
black: 1922
When you add 50 million people to a delta
(Nile), you do not want channel avulsions
and shifting, particularly when valuable
infrastructure is at risk (e.g. Vancouver Intl
Airport). So you reduce the number of
channels, and engineer the flow of water.
Syvitski 2015, IAHR
Fraser Delta Canada
Stored Runoff
< 2% annual flow
2
10
25
50
100
> 100%
Vorosmarty et al, 2003
Water engineering distorts a river’s
flow and timing, with delays,
diversions, storage — providing for
unusual hydrographs & sediment
sequestration
Syvitski 2015, IAHR
The global location of very large dams.
Note 1952 and China’s Great Leap forward.
YEAR
Movie credit: CSDMS
On average we build one large dam every day
And for the last 130y !
Syvitski 2015, IAHR
Modification of the world’s
hydrological system continues
to accelerate, and thus so do
floods due to engineering
failure
Syvitski 2015, IAHR
Engineering has
reduced the amount of
freshwater entering our
delta systems
Indus
108
Evaporation
Indus at
Guddu
Domestic Use
1
3
56
Evaporation
Canal Diversions
52
River
Losses
45
SEA
27
22
Diversion to Fields
6
Groundwater
Recharge Discharge
1
4
17
4
8
11
Soil Evaporation
2
Crop Use
Evapotranspiration
Water Balance (km3) for the Sindh Province:
after Azad 2003, FAO
Milliman, 2008
Leading to: reduced biodiversity; saltwater intrusion,
salinization of soils; and increased coastal salinity &
temperature.
Syvitski 2015, IAHR
Engineering has
also reduced the
amount of
sediment entering
our delta systems
Wang et al., 2007
Huanghe is an
example of its
sediment load
returning to
pristine levels
through
engineering
Wang et al., 2007
Syvitski 2015, IAHR
3% S Spain
22% S Spain
Liquette et al., 2004,
Oceanography
Ebro R.
Water
1913-62:
1965-85:
1988-90:
1732
429
300
m3/s
Sediment
MT/y
18
2
0.2
Since 1983, 110 MT of sand
have been delivered by trucks to
the Spanish shores to ease the
rate of coastal retreat.
71% S Spain
Once the World’s Rice Bowls
Ramankutty et al.
Nile
Indus
Proportion
Land in Crops
Mekong
Ganges
Syvitski 2015, IAHR
Deltas have transformed to
become our Protein Bowls
Mekong delta, Vietnam
Wisdom Project/DLR (2009)
1,000,000 tons of
shrimp per year!
Pearl River delta, China
Courtesy of Mark Bender
Syvitski 2015, IAHR
Destruction
of
mangrove
forests for
shrimp
farms
hastens
shoreline
retreat
3
To Sink or Not to Sink
The Balance
Shrimp & Fish Farms
Syvitski 2015, IAHR
Delta Surface Elevation Processes & Rates
(Syvitski et al, 2009 Nature Geoscience)
Eustasy (1-6 mm/y)
(Increase in ocean volume by surface-ocean
warming & ice melt
Aggradation (0-10 mm/y)
(New layers of sediment added)
Load Isostasy
(0.2–3 mm/y)
(weight of shelf water &
sediment deposit)
Natural Compaction
(0.3 – 3 mm/y)
Human-induced Subsidence (0 – 250 mm/y)
(petroleum & water mining, peat oxidation)
Delta Surface Elevation
ΔRSL = A - ΔE - Cn – CA ± M
Each term is spatially and temporally variable, between deltas and
within a delta.
Syvitski 2015, IAHR
10 21st Century Aggrada+on Rate mm/y 9 8 7 6 Fly
5 Limpopo
4 3 Magdalena
Ganges
Amur
2 1 Tigris
Godavari
Indus
Danube
Krishna
0 0 1 2 3 4 5 6 7 19th Century Aggrada+on Rate mm/y Syvitski 2015, IAHR
8 9 10 Saito et al., 2008
1958-1962
Deltares, 2012
118° E
30'
119° E
30'
30'
Bohai Sea
30'
Yellow
Delta
Deformation mm
38° N
River mouth
Laizhou Bay
37° N
Distance from pump (m)
25 km
Subsidence at fish farms is up to 250 mm/y due to groundwater extraction
Higgins et al., 2013, GRL & Higgins, S. (2014)
Syvitski 2015, IAHR
Humans are sinking deltas 4x faster than sea level is rising
Nile
Vistula
Syvitski et al, 2009, Nature Geosciences
Syvitski 2015, IAHR
4
Consequences & Adaptation
Public Alarm
Inundation & Shoreline Erosion
Coastal Barriers & Failures
Adaptation
Syvitski 2015, IAHR
Sinking Deltas in the Press
Syvitski 2015, IAHR
Sinking Deltas
in the Press
Syvitski 2015, IAHR
Sinking
Deltas
in the Press
Syvitski 2015, IAHR
Mississippi Delta, 1984-2012, LandSat
Syvitski 2015, IAHR
Indus Delta 1935 - 2000
1944-2000
Syvitski 2015, IAHR
Starved of
sediment,
erosion
dominates
the modern
Indus Delta.
New
estuaries
and tidal
channels
have
formed, and
tidal flats
have
extended
landward.
The Chao Phraya Delta shoreline has retreated 1 km in 50 years.
Rokugawa et al., 2006; Saito et al., 2007
Syvitski 2015, IAHR
11,000 km
Syvitski 2015, IAHR
Storms, Storm Surges and Floods are killers.
Every year levees in the GBM
delta need of repair, as the
dynamic channels churn up the
landscape. Photo credit. Irina Overeem
Ganges-Brahmaputra Delta
CSDMS Inundation Map
Cyclone Aila, May 2009,
caused extensive GBM
flooding, as the storm surge
reached 6-7m
Syvitski 2015, IAHR
San Joaquin Delta
Mississippi Delta
Even in rich countries,
infrastructure failures are common
New Orleans
Rapid Drawdown
induced failures
(Mississippi Delta)
Syvitski 2015, IAHR
Vietnam
Amazon
Countries need to consider
methods of adaptation
Germany
Netherlands
Syvitski 2015, IAHR
Fight or Flight = Protect or Get out of the Way
USA
Bangladesh
Deltas hold 500+M people, are highly productive, biodiversity hotspots,
filters, repositories & reactors for water, sediment, carbon, nutrients,
pollutants. They are megacity hubs, and ports, and offer waterway transport.
Ecosystem services include forestry, fisheries and agriculture. Human
interventions put deltas in peril through flooding, shoreline retreat, land
subsidence, saltwater intrusion, and saline soils. Food security is threatened,
infrastructure repairs need ever increasing resources for coastal protection.
Syvitski 2015, IAHR