Channel Change Along the Amite River – A GIS Analysis

ASSESSING HUMAN IMPACTS ON
FLORIDA’S RIVERS:
WHY MORE VARIABLES MATTER
Joann Mossa
Department of Geography, University of Florida
BACKGROUND
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Those who cannot learn from history are doomed to repeat
it. George Santayana
We have many examples of impacts to rivers in Florida that
were largely unintended
Regulators concerned with impacts largely use minimum
flow levels (MFLs) and total maximum daily loads (TMDLs)
to protect aquatic systems
Using examples, I will illustrate that other variables matter
These groups of variables include:
 floodplain inundation measures
 minimum stage or water levels
 minimum velocity levels
 channel instability measures
FLOODPLAIN INUNDATION
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In alluvial rivers, inundation
occurs at the bankfull stage
upon which connection
between the channel and the
floodplain occurs
Inundation affects wetland
health, allows for migration of
organisms, exchanges of
nutrients
Example demonstrating
importance of floodplain
inundation is channelized
Kissimmee River
http://www.saj.usace.army.mil/dp/Kissimmee/FL_map_KRR.bmp
TEXTBOOK RIVER:
FREQUENCY OF DIFFERENT FLOWS
Source: Leopold,
Leopold, 1984
http://www.tommymarkham.com/Hurricane/KissRivat70in1947A.jpg
BEFORE AND AFTER CC-38
SR70
Highlands South 1958
Highlands South 1970
PRE- & POSTPREPOSTCHANNELIZATION,
KISSIMMEE RIVER:
WETLAND PLANT
COMMUNITY
DISTRIBUTION
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The project
reduced floods, but
not without a price
Lost 8000 ha of
wetlands
From: Toth et al., 1995
HISTORIC KISSIMMEE WAS
ECOLOGICALLY RICH
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Haven for wildlife
at least 39 species of fish
and 38 species of water birds
POST-CONSTRUCTION OF CPOSTC-38:
IMPACTED WATER BIRDS
DIMENSIONLESS FLOW DURATION CURVES:
KISSIMMEE RIVER (PRE & POSTPOST-CANAL)
10
Ratio of Q to Bankfull Q
Kissimmee River at Okeechobee
1
0.1
0.01
1930-1959
1970-1999
0.001
0.0001
0.01
0.1
1
10
30
50
70
90
99
99.9
99.99
Percent of time flow exceeded
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Ratio of 1 is where the discharge equals the bankfull Q
Ratio of 10 suggests the max Q is ten times bankfull Q
The historic Kissimmee River was above bankfull 30% of time
The channelized Kissimmee did not exceed bankfull
RECOMMEND THAT WE PAY ATTENTION TO THE MAGNITUDE,
FREQUENCY AND DURATION OF ABOVEABOVE-BANKFULL FLOWS
STAGE OR WATER LEVEL
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http://www.flickr.com/photos/hotash/80130901/in/set--1712265/
http://www.flickr.com/photos/hotash/80130901/in/set
In ongoing water battles,
minimum flow level should
not be the only measure
evaluated. Reservoir
construction, creation of
several artificial cutoffs
and dredging locally
reduced the stages or
water levels in the
Apalachicola River.
Consequently, there is
less water and flow in the
secondary channels
flowing across the
floodplain than historically
because the waters in the
main channel are now
lower in elevation. Thus,
the local water level also
matters to aquatic biota.
STAGE (FOR FLOWS NR 10000 CFS)
APALACHICOLA RIVER AT CHATTAHOOCHEE,
1929--95
1929
Low flow stage went
from 47 to 42 ft since
1950s
Source: Light, Darst and Grubbs, USGS PP1594, 1998
River Styx
DISCONNECTED
FLOODPLAIN
STREAM, RM 59.7
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Currently
connected at flows
>16,000 cfs
Source: Light, Darst and
Grubbs, USGS PP1594,
1998
SECONDARY CHANNELS HAVE LESS WATER WHEN
WATER LEVEL IS LOWER
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River Styx is
disconnected from ACF
during low flow
Source: Light, Darst and Grubbs,
USGS PP1594, 1998
WATER LEVEL DROP: INCREASED WIDTH
AND SIMILAR BED ELEVATION
Source: Beidenharn, 2007
Time 1
Time 2
MINIMUM
VELOCITY LEVELS
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When flow velocities
(different from but correlated
with flow levels) are fines and
organics will settle
Abandoned portions of the
Kissimmee River now
undergoing restoration
contain thick deposits of fine
and organic material that
settled on a sand bed due to
lack of sufficient flow
velocity.
Concerns about impacts of
excess organics to Lake
Okeechobee
BOTTOM SEDIMENTS IN REMNANT
CHANNELS
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Assumed
Pre CC-38
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Assumed
Post CC-38
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Where will it go?
http://en.wikipedia.org/wiki/Image:Okeechobee_lake.jpg
CARACARA RUN
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Thick deposits of fines
and organics
Fine + organic
CHANNEL
INSTABILITY
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Where a channel is highly unstable, the
surface hydrology and local
ecosystems can be drastically altered.
In the panhandle at Big Escambia
Creek, floodplain sand and gravel
mining resulted in an avulsion. Tthe
original river was abandoned, greatly
altering the local habitat for nonmigratory species.
It also caused excessive sedimentation
on the Escambia River with likely
environmental and possible engineering
consequences there.
A large restoration project put the
channel back in its place, although
impact assessments and monitoring of
this project have been limited.
PLANFORM
Source: Leopold, 1994
CROSS SECTION
PROFILE
BIG ESCAMBIA CREEK
Photorevised 1987
Big Escambia Creek
Happy Valley
Escambia River
Adjusted Stage and
Mean Bed Elevation (m)
ESCAMBIA RIVER NEAR CENTURY
1978
20
15
10
5
0
-5
1930
1940
1950
1960
1970
1980
1990
2000
2010
2000
2010
ESCAMBIA RIVER NEAR
Year CENTURY
Width-Depth Ratio
500
400
300
200
100
0
1930
1940
1950
1960
1970
Year
1980
1990
OTHER PLACES HAVE
MORE SEVERE PROBLEMS
WITH INSTABILITY:
AMITE RIVER, LOUISIANA
Political boundaries are “fixed”,
channel isn’t!!!
ADDITIONAL COMMENTS
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Richter…How much water does a river really
need?, IHA software
Everglades-quantity, quality, timing and spatial
distribution…are we fully looking at all the
necessary variables for success of a project
costing >$10 Billion?
CONCLUSIONS
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There is regulatory concern about:
 minimum flow levels
 total maximum daily loads
At least four other GROUPS OF VARIABLES should
be considered in regulation of Florida’s rivers and
surface waters
Many engineering projects have unintended
consequences, and with more measures to assess
the potential consequences, we can better assess
how these compare to potential benefits
MEAN VALUES FOR BASIC HYDROLOGIC PARAMETERS NEAR 36 VERY
LARGE DAMS (Graf 2006)
AVULSIONS
TOTALS
Number of Mine
Pits
Disturbed Area
Number of Point
Bars
Area of Point Bars
1980/1984
1998
236
325
23,466,587 m2
34,336,980 m2
130
183
2,867,849 m2
4,262,838 m2
Point Bar Area vs. Reach Blocks
Point Bar Area (sq. meters)
500000
400000
300000
200000
100000
0
0
10
20
30
40
50
Reach Blocks
Old Point Bar Area
New Point Bar Area
60
USING CENSORED STAGES (OMIT FLOODS OR
DISCHARGES ABOVE A SELECTED VALUE)
Adjusted Stage and
Mean Bed Elevation (m)
ESCAMBIA RIVER NEAR CENTURY
20
Stage
Stage
MBE
MBE
15
10
5
0
-5
1930
1940
1950
1960
1970
Year
1980
1990
2000
2010
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Quotable
"If a child is to keep his inborn sense of
wonder...he needs the companionship of at
least one adult who can share it..."
-- Rachel Carson
HIGH AND DRY
Source: Light, Darst and Grubbs, USGS PP1594, 1998
MONTSDEOCA CONNECTOR
E levation R elative to L eft
Monum ent (m )
Monts deoc a C onnec tor - 01
5
4
3
2
1
0
-1
-2
-3
-4
-5
0
20
40
60
80
100
Dista nc e from L e ft Monum e nt (m )
E levation R elative to L eft
Monum ent (m )
Monts deoc a C onnec tor - 02
5
4
3
2
1
0
-1
-2
-3
-4
-5
0
20
40
60
Dista nc e from L e ft Monum e nt (m )
80
100
MONTESDEOCA RUN-CONNECTOR
Wetted Channel Dimensions
3.5
Remnant "D"
3
Recarved
Connector
Depth (m)
2.5
Restored
Remnant "A"
2
1.5
1
0.5
0
0
10
20
30
40
50
Width (m)
60
70
80
90
“Sand bars are bad!”
Paul Hartfield, USFWS
Quoted Nov. 2001
On canoe trip on Chicksawhay
River south of Enterprise
SAND BARS COULD BE “BAD” IF THEIR SIZE AND
ABUNDANCE IS A SIGN OF MARKED DISTURBANCE
Post--settlement alluvium
Post
Buried soil
Widely known that basin land use changes (e.g. deforestation) can
accelerate floodplain sedimentation forming post-settlement alluvium.
Increased sediment supply from the basin or from bank erosion due to
changes in runoff could also cause sand bar area to increase
OFTEN SAND BARS ARE ASSOCIATED WITH “BAD” THINGS
SUCH AS EROSION ON THE OPPOSITE BANK
SAND BAR ON UPPER CHICK
CORRESPONDS WITH UNSTABLE
OPPOSITE BANK
Bogue Homo Point Bars
Cumulative Downstream Area (m2)
250000
1955
1996
200000
Cumulatively, the Bogue Homo had more
sand bar area in 1955 than 1996
150000
100000
50000
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Dista nce (km)
Thompson Creek Point Bar Area
Downstream Cumulative Area (m2)
250000
1955
1996
200000
Cumulatively, Thompson
Creek had about 2-3X more
sand bar area in 1996 than
1955
150000
100000
50000
0
1
2
3
4
5
6
7
8
9
10
11
Distance (km)
12
13
14
15
16
17
18
19