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Home , Flood pulse concept, Shoal

Implications of Channelization and Sedimentation on Bottomland Hardwood

Aaron Pierce, Ph.D. Louisiana State University

Hydrology

• Single most important factor affecting function • Influence plant structure, composition, invert communities and wildlife

Hydroperiod

• Seasonal pattern of water level in a wetland • Defines the rise and fall of a surface and subsurface water levels

1 Wetland Hydroperiod

Seasonal pattern of water level in a wetland.

Hydrologic Signature

Depth Ground Time Surface 3 Components: 1) duration: Average or total amount of time standing (6 COE Zones) water exists during a flood event. 2) Flood frequency: Average number of times a wetland has standing water per year. 3) Flood depth: Depth of aboveground standing water.

Hydroperiod Variability

• General patterns over long-term but highly unpredictable within and among years • Natural variability is essential to maintain system productivity

Flood Pulse Concept • Lateral connectivity of a and its is critical for productivity of river, forests, and its organisms • Life-cycles of floodplain plants and animals and many floodplain functions (e.g., retention) are linked to flooding patterns

2 Dynamic Hydrology of Hardwood Bottomlands

Day 1 Day 5

Natural hydroperiod is characterized by stochastic and ephemeral flooding events

Unaltered Systems

Geomorphology • are formed from the and of sediment • Patterns and rates of erosion and deposition are critical forces affecting wildlife Where is natural scouring and and fish deposition occurring?

3 Sedimentation • Provides sediment retention, improves water quality, replenishes nutrients, and creates new areas for colonization by wetland plants

Point deposition – within • creates ridge and topography • temporary storage of sediment

Vertical Accretion – deposition in the floodplain • results from overbank flooding • forms the primary floodplain • rates and textures are highly variable

Overbank Sedimentation

• Deposition rates typically <1 cm/yr • Most deposition occurs near the stream channel • Depressional areas can also receive high rates of deposition

Geomorphology and Vegetation

Black Gum White Oak Live Oak Loblolly Pine Water Hickory Overcup Oak Hickories Overcup Oak Green Ash Water Oak Red Maple Cow Oak River Birch Green Ash Cherrybark Oak Black Willow Water Elm Sweetgum Cottonwood Water Tupelo Willow Oak Baldcypress High Ridge Low Flats Back- Ridge High swamp Low Ridge Ridge Oxbow Stream Channel First Bottom Second Bottom From Conner 1994

4 Activities Impacting Wetlands

• •Highways • Irrigation • • Oilfield • Channelization

Reasons for Channelization

• Mainly for agricultural purpose to remove water from land for cultivation

Channelization

• Straightens, shortens, and steepens stream channels • Increases stream velocity and stream power • Facilitates transport of to the river system • Impacts hydrology and geomorphology

5 Hydrologic Impacts

• Alters timing, depth, duration, and frequency of flooding • Disconnects from the floodplain • Can cause excessive ponding at

Geomorphic Impacts

• Excessive sediment deposition, increased overbank flooding, increased water table, degrade bottomland systems

Hatchie River • Headwaters are in Upper East of Mexico • Drains into MS River • Longest unchannelized stretch of river in LMAV

6 Hatchie River • Supports 100 species of fish, 250 species of birds, 50 species of mammals, 35 species of mussels, and numerous herps • Globally rare Hatchie River burrowing crayfish • TNC "Last Great Place" list

http://www.hatchie.com/index.html

BLH Forests

• Structurally diverse • Highly productive • Important timber resource and provides important wildlife and fisheries habitat

Economic Value

• Over $3.6 billion generated by timber industry in West TN in 1997 • BLH are an important component of regional and state economy

7 BLH Losses

Arkansas Arkansas Tennessee Tennessee Mississippi

Louisiana Louisiana

System Alterations • Extensive channelization of over 90% of the • Altered hydrology caused rapid geomorphic adjustment

Root of the Problem

• Geology – Source of the sand • Past and Present Land Use – expose the sand

Thin Fertile Loess Layer with Underlying Sand

8 Erosion

Channel Erosion

Jeffers Creek

9 Transport

Fine and Clays

Coarse Sand

Valley Plugs • Occur where sediment (sand) laden waters slow in velocity • Debris jams and intersections of tributaries and rivers are common locations • Completely plugs the channel • During subsequent flows, the plug enlarges upstream as additional sand is deposited

10 Plug

Unaltered

Valley Plug Formation

Bear Creek Channel Profile Distance upstream from VP and Channel Depth

0.4 Filled at Valley Plug

0 01234567899

VP -0.4 50m 100m

(m) 150m 200m 250m -0.8

-1.2 Full channel depth at 250 m

-1.6 (m)

Possible Impacts • Increases in the water table height • Shift in floodplain plant species composition • Homogenizes aquatic • Alters flood frequency Hickory Creek – valley plug

11 Overbank Flooding

Excessive Deposition

Sand Splay

Telephone Pole Effect

Sanding of Timber

• Kills standing timber • Alters tree species composition •Buries productive soils

12 Ponding of Timber

• Increased water table and accelerated natural levee development encourage permanent ponding of timber

Abandoned Channel

• Reduced flooding and sedimentation leading to a shift in species composition

Shoal Sites

• sites may be impacted in similar ways as valley plug sites but to a lesser Tributary extent Intersection • Channel filling influences overbank flooding and the water table • Crevasse splays cause excessive deposition in the floodplain

13 Location of Study

Control Study Site Sampling Design

Upstream Tributary

50m

200m

= plots sampled for Downstream sediment deposition

Valley Plug Study Site Sampling Design

Downstream Abandoned Channel

200m = Valley Plug

= plots sampled for sediment deposition

50m Upstream

14 Feldspar Sediment Pads

Excessive Sand Deposition

0.78 meters

Early Fall

• Dendrogeomorphic approach to measure sedimentation • Provides a long- term average of sedimentation

Relate age with depth to root collar (tree base)

15 Mean Annual Deposition 2002-2004

Valley Plug Sites (4): A 6.0 • Mean = 5.46 cm/yr

•SE = 0.44 4.5 Shoal Sites (2): 10X • Mean = 0.57 3.0 Deposition •SE = 0.24 1.5

Control Sites (4): Annual Deposition (cm) B B • Mean = 0.46 cm/yr 0.0 •SE = .05 Valley plug Shoal Control

Geomorphic Feature

Maximum Annual Sediment Deposition Rates (cm/yr)

Valley Plug Sites 80

70

60

50

N 40 R R T , A A r e , , e k p r s 30 v e e i a t N L m iv i R a i T t S r o w R 20 n l u r o S e o f r o e l h t s t e k c s s e c a n Deposition Range (cm/yr) Deposition 10 i a o e R l C M C W B 0 Heimann & Hupp & McInyre & Hupp & Kleiss Pierce & Pierce & Roell 2000 Brazemore Naney Morris 1996 King 2004 King 2004 40X 1993 1991 1990 Study <2 cm per year

Deposition Texture Types

100% 90% 80% 70% Larger 60% Sediment 50% at VP 40% and 30% ! of Plots Percentage 20% 10% 0% Valley Plug Shoal

% Sand % /Sand % Silt

16 Deposition at Valley Plugs by Location

14

11 Where does 7 deposition occur?

4 Annual Deposition (cm) 0 1234

1 = upstream of vp, 2 = at vp, 3 = downstream of vp, 4 = control

Dendrogeomorphic Analysis

8 Why?? 7 valley plug 6 control 5

4 Greatest

3 Sedimentation with Youngest 2

Mean Deposition in cm/yr Trees 1

0 1840 1860 1880 1900 1920 1940 1960 1980 2000 Year of Tree Germination

Spatial Trends

Deposition In direction at Control of channel Site and in depressions

Low Deposition (<0.5 cm/yr)

Prediction Map 0 120 240 Meters Contours

0 - 0.19 cm/yr 0.20 - 0.47 cm/yr

17 Spatial Trends

Perpendicular to channel Deposition at Valley Plug High Deposition (>1 cm/yr)

Prediction Map 0 110 220 Meters Contours

0 - 0.76 cm/yr 5.80 - 11.19 cm/yr

11.20 – 41.55 cm/yr 0.77 - 1.52 cm/yr

1.52 – 5.79 cm/yr

Summary

• Deposition is 10 times greater at valley plug sites than at control and shoal sites • Significant differences in deposition types among types • Valley plugs are progressing upstream, impacting new areas • Valley plugs change the spatial dynamics of sedimentation

Future Work

• Investigate linkages between excessive sedimentation and changes in surface and subsurface hydrological regimes • Determine implications of excessive sedimentation, surface and subsurface hydrology on succession of BLH forests

18 Maximum Flood Depth and Total Duration of Flooding

Initial Findings 250 VP Sites Drier!!! 200 Why? 150

100

50

0 Bear vp Hickory vp Jeffers vp Marshall Spring Hatchie GVL Maximum Flooding Depth (cm) Total Duration of Flooding (days)

Abundance of Tree Species

Control SiteInitial Findings Valley Plug Site

Cypress, Oaks Maple Maple, Willow, Sweetgum

Oak

Elm

Ash

Cypress-Tupelo

Willow-Birch

Sweetgum

Hickory

Sycamore-Cottonwood

Others

Differences in Species Evenness!

Acknowledgements

• Funding provided Special Thanks : by the U.S. Fish Dr. Hupp and Wildlife Service and the U.S.D.A. – Dr. Tim Diehl CSREES: Initiative The Nature Conservancy for Future Agriculture and Food Systems.

Field Crew: Justin Nolte, Eric Sawyers, Chuck Yoest, Nick Wirwa, B.J. Wilson, Wes Cochran, Jimmy Fox, Jeff Roberson, and Nick Winstead

19 Questions?

Photograph by Byron Jorjorian

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