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