Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
U.S. Department of the Interior
U.S. Geological Survey
Nutrient and Sediment Cycling and Retention in Urban Floodplain Wetlands
Greg Noe, Cliff Hupp, Nancy Rybicki, Ed Schenk, and Jackie Batson
National Research Program, Reston VA
Funded by USGS Chesapeake Priority Ecosystem Science
Floodplain nutrient and sediment retention
What are nutrient cycling and sediment deposition rates?
What are the controls?
What is the percent retention of river loads by floodplains?
Floodplains are last location in watersheds for significant material retention before river loading into coastal waters
Coastal Plain floodplains trap large nutrient loads
1) Measured sedimentation fluxes in plots
2) Scaled to entire CP extent of floodplain
3) Compared to river load
Percent retention for 7 rivers:
Median Range
Nitrogen 22% (5 to 150%)
Phosphorus 59% (14 to 587%)
Sediment 119% (53 to 690%)
Noe and Hupp. 2009. Ecosystems.
g m-2 yr-1 × m2
g yr-1
Hydrogeomorphic controls in floodplain ecosystems
Four dimensions of river corridors influence floodplain ecosystem processes
through river-floodplain hydrologic connectivity
This heterogeneity is critical to the prediction and scaling
of floodplain effects on water quality
Noe. 2013. Treatise of Geomorphology. Modified from NRC 2002.
Difficult Run Floodplain Study measuring sediment and nutrient retention along lateral and longitudinal
floodplain gradients in an urban, Piedmont watershed
Noe. 2013. Treatise of Geomorphology.
0
2
4
6
8
10
12
14
16
1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
Urbanization influence on flooding N
um
be
r o
f fl
oo
ds
(dis
char
ge >
10
00
cfs
)
Hupp et al. in review
Difficult Run Floodplain Study measuring sediment and nutrient retention along lateral and longitudinal
floodplain gradients in an urban, Piedmont watershed
longitudinal gradients
lateral gradients
Ecosystem process measurements Mineralization CO2 flux Hydroperiod
Litterfall Sedimentation
Bank erosion
Annual net mineralization rates
downstream
Site
0 1 2 3 4 5
P m
ine
raliz
atio
n (
mm
ol-P
m-2
yr-
1)
-4
-2
0
2
4
6
8
Levee
Backswamp
Toe slope
Site
0 1 2 3 4 5
N m
ine
raliz
atio
n (
mm
ol-N
m-2
yr-
1)
0
100
200
300
400
500
600
downstream
Noe et al. in review
Turnover of soil N and P pools
Rate Areal mineralization (mmol m-2 yr-1)
Turnover rate
(mol mol-1 yr-1)
Turnover time (yr)
P mineralization 3.60 0.0027 369
N mineralization 319 0.046 22
% nitrification 66%
Noe et al. in review
Sedimentation stimulates mineralization
Estimated P sedimentation during incubation
( mol-P m-2 d-1)
10-1 100 101 102 103 104
P m
iner
aliz
atio
n (
mo
l-P
m-2
d-1
)
-10
0
10
20
30
40
R2 = 0.269 P < 0.001
1:1
N sedimentation during incubation
( mol-N m-2 d-1)
100 101 102 103 104 105
N m
iner
aliz
atio
n (
mo
l-N
m-2
d-1
)
-2000
-1500
-1000
-500
0
500
1000
1500
2000
2500
R2 = 0.120 P = 0.010
1:1
Noe et al. in review
Plant uptake vs. mineralization
N mineralization ( mol-N m-2 d-1)
0 500 1000 1500 2000 2500
Veg
etat
ion
N u
pta
ke
litte
rfal
l an
d h
erb
aceo
us
(m
ol-
N m
-2 d
-1)
0
500
1000
1500
2000
25001:1
r = 0.371P = 0.052
P mineralization ( mol-P m-2 d-1)
0 20 40 60 80 100
Veg
etat
ion
P u
pta
ke
litte
rfal
l an
d h
erb
aceo
us
(m
ol-
P m
-2 d
-1)
0
20
40
60
80
1001:1
r = 0.057P = 0.775
Rybicki et al. in prep.
Site
0 1 2 3 4 5
N s
edim
en
tation
(g m
-2 y
r-1
)
0
5
10
15
20
25Levee
Backswamp
Toe slope
Site
0 1 2 3 4 5
P s
ed
ime
nta
tio
n (
g m
-2 y
r-1
)
0
1
2
3
4
5Nutrient sedimentation rates
downstream
N S
edim
enta
tion (
g m
-2 y
r-1)
0
5
10
15
20
25
30
Chickahominy
MattaponiPocomoke
Roanoke
Mill Stream Tangipahoa VA Piedmont Difficult
P S
edim
en
tatio
n (
g m
-2 y
r-1)
0
2
4
6
8
10
Chickahominy
Mattaponi
Pocomoke RoanokeMill Stream Tangipahoa Difficult
Geomorphic controls on sediment retention and loss
Hupp et al. in review
Site 0 Site 1 Site 2 Site 3 Site 4 Site 5
Sed
imen
t g
ain
or
loss
(k
g m
-1 y
r-1)
-500
0
500
1000
1500
Floodplain
Banks
Net
Site 0 Site 1 Site 2 Site 3 Site 4 Site 5
Flo
od
pla
in T
rap
pin
g F
acto
r
-20
-10
0
10
20
30
40
50
60Net trapping factor
Gross trapping factor
41% of mainstem length impounded
Dam locations from FCPA
Historic mill dams and legacy sediment
Hupp et al. in review
2.5 m
Plank road
4.47 0.11
7.08 0.65
g m-2 yr-1 (average all floodplain plots)
N net flux = + 11.43 P net flux = + 2.35 Sediment net flux = + 3984
2.66 0.54 1092
14.09 2.89 5076
Urban, Piedmont floodplain is retentive
Noe. 2013. Treatise of Geomorphology.
Correlations among ecosystem processes
Hydroperiod
N sed.
N mineralization
N plant uptake
DIN load
CO2 flux
P sed.
P mineralization
P plant uptake
SRP load
Nutrient and Sediment Cycling and Retention in Urban Floodplain Wetlands
Urban floodplain wetlands can still remove pollutants • Despite legacy sediment, mill dams, and stormwater • High nutrient and sediment inputs • Efficient internal cycling of nutrients • Coupled N and P biogeochemical processes • High trapping rates relative to watershed losses
U.S. Department of the Interior
U.S. Geological Survey
ABSTRACT DEADLINE: 12 July 2012 (23:59 ET)
Tidal freshwater rivers link watersheds with estuaries and affect the flux
of carbon, nutrients, sediment, and freshwater from land to the ocean.
However, climate change is continually altering tidal river ecosystems as
tides advance inland and watershed inputs change. This Chapman
Conference will generate synthesis of feedbacks between geomorphic,
biogeochemical, and ecological processes in tidal rivers to better predict
ecosystem changes in response to climate change.
www.agu.org/TidalRivers