Large River Flood Pulse

N

Where Are We?

Barataria

Terrebonne

Ponchartrain

Atchafalaya

Habitat Types of the Barataria-Terrebonne Basins

The Floodplain Extends to the Coast

• All flowing Louisiana waterways eventually drain to the Gulf of Mexico

• How much are energy and nutrients transferred throughout the estuary?

• Is the coast is ultimately supported by floodplain ecosystem processes

How Connected are the Swamps to the Coast?

Estuary Continuum?

Estuaries

Swamps and marshes

Tropical rain forest

Temperate forest

Northern coniferous forest (taiga)

Savanna

Agricultural land

Woodland and shrubland

Temperate grassland

Lakes and streams

Continental shelf

Open ocean

Tundra (arctic and alpine)

Desert scrub

Extreme desert

800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600

Average net primary productivity (kcal/m2/yr)

Net Primary Production(measure of available energy and nutrients)

(Miller, G.T. 2002. Living in the Environment: Principles, Connections, and Solutions)

Stream Order

11

11

22 22

11

11 11

33 22

Stream Order – Strahler MethodStream Order – Strahler Method

Used to classify a stream in relation to tributaries, drainage area, total length, and age of water.

1 1 = 2

1 2 = 2

2 2 = 3

1 3 = 3

2 3 = 3

3 3 = 4Mississippi River is classified as a 10th or 12th order stream.

Headwater stream classification matters

Major Rivers of The World

NameDischarge 103 m3/sec

Length 103 km

Drainage Area 106 km2

Amazon, South America 212.40 6.44 5.78

Congo, Africa 39.65 4.70 4.01

Ganges-Brahmaputra, India 38.50 2.90 1.62

Yangtze, China 21.81 5.98 1.94

Yenisei, USSR 17.39 5.54 2.59

Mississippi, North America 17.30 (6) 6.02 (3) 3.22 (4)

Mekong, Asia 11.04 4.00 0.80

Nile, Africa 3.10 6.65 3.35

Rivers and Streams

• Generally represent the excess of precipitation on land areas over evaporation from them.– Precipitation that falls is either evaporated,

transpirated, enters the ground water supply, or flows down rivers

• Flow is down-hill and varies seasonally– Related to rainfall and ice/snow melt

• Beginning of a river = the source and the end of a river = the mouth

• Discharge - volume of water passing a given point during a period of time– Channel Width X Depth X Velocity

Rivers and Streams

• Materials are transported by running water in three principal states– Dissolved matter– Suspended solids– Bed load

• Allochthonous – organic material brought in from outside the system

• Autochthounous – organic material produced within the system (primary production)

Maringouin: 6,000 – 7,000 years ago Teche: 5,700 – 3,900 years ago St. Bernard Delta: 4,600 – 1,800 years ago Lafourche Delta: 3,400 - 400

Construction of levees along the Mississippi River and many of its tributaries has severed the river from over 90% of its floodplain, denying fish and other aquatic species access to millions of acres of foraging, spawning and nursery habitat.

Miss. Dept. of Archives and History

Miss. Dept. of Archives and History

http://www.lmrcc.org/ARMP%20folio.pdf

The Flood Pulse

1959-2005 Atchafalaya River Stage at Butte La Rose USACE Gage ID = 03120

0

1

2

3

4

5

6

7

8

9

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Avg

. M

on

thly

Riv

er S

tag

e (m

)

= Average Stage

= 2005 Stage

September

December

February

April

AprilJuneAugust

September

Floodplain Zones

From Larson et al. 1981; Hall and Lambou 1990

I II III IV V VI

Aquatic Ecosystem

Active Floodplain

Floodplain Upland Transition

Terrestrial Or Upland Ecosystem

Bottomland Hardwood Ecosystem

Floodplain System

Mississippi River (Main Stem)

Atchafalaya River (Distributary)

Flow

Distributary – A smaller channel that takes water away from the main stem river.

Atchafalaya River Basin

ARB Cross Section

Atchafalaya River

Natural LeveesFloodplain Floodplain

Protection Levees

Back Water Area Back Water Area

FloodplainDeer Lake

Billy Littles Lake

Bank Full Level = 66 ±

9.5 cm

AR = 218 cm (7.15 ft)

Lake

Staff Gage

Floodplain

Water Level

Atchafalaya River Basin

Three General Types of Water

• Brown– High flow, lots of sediment, fairly high oxygen

levels, riverine

• Green– Low flow, stratification, very high surface

oxygen levels, highly productive, lacustrine

• Black– Low flow, very low surface oxygen levels, not

productive, swamp

Backwater Interior Lakes Mainstem

December

June

August

What is Hypoxia

• Dissolved Oxygen less than 2.0 mg/L

• Normoxic = DO > 2.0 mg/L

• Generally, most fish can not tolerate hypoxic conditions for long periods.– Gar, bowfin (choupique), bullheads can

When and Where Is Hypoxia?

• Generally found during high water times when temperatures are warm.

• Backwater areas (away from the mainstem river).– Low flow

Oxygen Level Controls

Photosynthesis produces oxygen:Solar Energy + CO2 + H20 C6H12O6 + O2

Respiration consumes oxygen:C6H12O6 + O2 CO2 + H20 + chemical energy(ATP)

Aquatic/Terrestrial Transition Zone

(ATTZ)• Alternates between

aquatic and terrestrial habitats (active floodplain).

• Important for fish feeding and reproduction.

• Facilitates transfer of energy and nutrients between aquatic and terrestrial habitats.

Terrestrial Vegetation Growth During Low Water

Nutrients Released During High Water

Simply put:

More Nutrients = More Plants = More Animals

Inundation of the floodplain is the mechanism of energy and nutrient transfer from terrestrial vegetation to the aquatic community.

= Happy Cajuns!!

Eventually the swamp drains and backwater areas become very productive.

Altered Flood Pulse

6

7

8 9

How Do ‘Unproductive’ Areas Support Living Populations?

• Detritus-Based Production– Decomposers (e.g., bacteria) transfer energy

stored in old organic matter to consumers• Insects, crawfish

– Low-oxygen tolerant organisms• Gar, bowfin (choupique), bullheads

Energy flow through an aquatic ecosystem.

From Cole 1988, Waveland Press

Detritus based energy flow through an aquatic ecosystem.

From Cole 1988, Waveland Press

What If There is no Flood Pulse?

• Barataria-Terrebonne National Estuary has been cut-off from the Mississippi River

• Hydrology is strictly related to local precipitation– What are the possible implications in light of

the Flood Pulse Concept?

No More Flood Pulse

Barataria

Terrebonne

Ponchartrain

Atchafalaya