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 8001,6002,4003,2004,0004,8005,6006,4007,2008,0008,8009,600 Average net primary productivity (kcal/m 2 /yr) Net Primary Production (measure of available energy and nutrients) (Miller, G.T Living in the Environment: Principles, Connections, and Solutions)

Stream Order Stream 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 = 4 Mississippi River is classified as a 10 th or 12 th order stream. Headwater stream classification matters

Major Rivers of The World Name Discharge 10 3 m 3 /sec Length 10 3 km Drainage Area 10 6 km 2 Amazon, South America Congo, Africa Ganges-Brahmaputra, India Yangtze, China Yenisei, USSR Mississippi, North America17.30 (6)6.02 (3)3.22 (4) Mekong, Asia Nile, Africa

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,

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

The Flood Pulse Atchafalaya River Stage at Butte La Rose USACE Gage ID = = Average Stage = 2005 Stage

September December February April

June August September

Floodplain Zones From Larson et al. 1981; Hall and Lambou 1990 IIIIIIIVVVI 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 Levees Floodplain Protection Levees Back Water Area

Floodplain Deer 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

BackwaterInterior LakesMainstem 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 + CO 2 + H 2 0  C 6 H 12 O 6 + O 2 Respiration consumes oxygen: C 6 H 12 O 6 + O 2  CO 2 + H 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

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