Many originate from
snowmelt in mountains
Runoff provides rivers with
Three “stages”, varying in
temperature and velocity
• Youthful (erosion zone)
• Mature (transport zone)
• Senile (deposition zone)
Youthful stage
(Upper course)
Senile Stage
(Lower course)
 Drainage
for agricultural use
 Drainage for manufacturing use
 Redirection
 Damns
 Pollution
What are they?
Why are they important?
What are wetlands?
The U.S. Fish and Wildlife Service defines wetlands as
the “…lands transitional between terrestrial and aquatic
systems where the water table is usually at or near the
land surface or the land is covered by shallow water.”
(Cowardin et al., 1979)
Wetlands must have all of the following characteristics:
Hydric soil
Hydrophytic vegetation
Standing water for at least part of the year
Types of wetlands
Forested wetland
Wet Meadow
Bog and fen
marshes – variable salinity
 Tidal salt marshes - saltier water
 Everglades
 Brackish
largest freshwater marsh in U.S.
Historical perspective on wetlands
The U.S. total of natural wetlands is estimated at 127
million acres
By 1950 45 million acres (35%) had already been
Presently only 10-19% of the area are wetlands (see
Most wetlands were lost to agricultural expansion
Some were lost to development due to population growth
They were considered wastelands and destroyed until
recent scientific research and environmental awareness
stressed their importance
Why are they important?
Hydrologic value—refers to the distribution and
movement of water on or below the earth’s surface
-wetlands are capable of slowing down and
retaining water (especially important
during floods or heavy rain)
-wetlands play an important role in
groundwater recharge
-plants along bodies of water slow down
sediment deposits in streams and lakes
(process called erosion) thus improving
water quality
Wetland importance…
Habitat value—wetlands are some of the most
biologically rich ecosystems in the world comparable to
tropical rainforests and coral reefs
-wetlands provide habitats for amphibians, fish,
wildlife, birds and plants
-some of the species can only survive in the
wetland environment
-there are 500 species of plants and animals
threatened with extinction in Illinois; 55% of
these depend on wetlands or other aquatic
habitats for survival (spotted turtle, Illinois
chorus frog, four-toed salamander, blackcrowned night heron and many more)
Wetland importance…
Direct use
--production of
saw timber and
Wetland importance…
 Water
--wetlands remove
pollutants from surface
runoff and streams
--wetland plants
reduce algae bloom and
fish kills by transforming
nitrogen and phosphorus
into available forms
Did you know that…?
Wetlands are often referred to as “the kidneys of the
landscape” because they filter out harmful materials
 One acre of wetland can store 1-1.5 million gallons of
 Wetlands comprise only 5% of the contiguous U.S.,
although they are home to 31% of all plant species
 As many as 50% of North American bird species either
nest or feed in wetlands
Threats to Wetlands
“Improvement” of wetlands drained and cleared
20% of the wetlands (1 Million
acres!) around New Orleans have
been lost over the last 100 years
Read more about it at:
Residential & Commercial
Federal regulations now in place
to prohibit destruction of wetlands
New Orleans : Areas Below Sea Level
Erosion of Lake Ponchartrain (meters per yr)
River System
Protection Against Hurricanes
Floods replenish land and soil and build new
land from sediments and deposits
Mississippi Delta and Barrier Islands act as a
buffers that slow down storm surges
Marshes, swamps, bayous and wetlands act as
sponges absorbing energy and water from
Freshwater Wetlands
Healthy Marsh
Atchafalaya Bayou
Chandeleurs Prior Katrina
Barrier Island
Chandeleur Barrier Islands
History That Contributed to Tragedy
1879: Congress authorized ACE to build levees
to prevent Spring flooding
Oil Industry and other development drained,
dredged, and built channels and canals
throughout wetlands and marshes
Mississippi River was channeled to empty at
continental shelf
Effects of Levees on Mississippi: in Missouri
New Orleans sank further below sea level as
earlier sediments and deposits compacted and
sank (no new sediments deposited)
Mississippi Delta and Barrier Islands began to
disappear – erosion and subsidence
Wetlands and marshes were fragmented, ripped
up, and destroyed, leading to recession of
Historic Deltas
Channeled Mississippi Delta
Dredging Marshes and Wetlands
Levees to Prevent Flooding
Canals Protecting Neighborhoods
Delta Community
Human-Made Channels
Sand Mining
Oil and Agriculture
Petro Channels Through Marsh
Environmental Impact Prior to Katrina
Rate of disappearance of wetlands:
1 acre every 24 minutes
60 acres per day
25 to 30 square miles per year
By 2050 Louisiana would lose another 1000 square
miles of marshes
By 2090, some estimates predict that New Orleans
will have sunk to approximately 10 to 15 feet below
sea level and that the coastline may have receded to
a point north of New Orleans
Erosion on Barrier Islands
Erosion of Delta and Barrier Islands
Disappearing and Sinking Wetlands
Disappearing Marsh
Erosion: Louisiana Coast
Recent History
1980s: 5 federal agencies & 6 state agencies have
jurisdiction: turf wars
LSU scientists model Katrina disaster
1990s: $40 million per year for remediation
1998: Hurricane Georges; New Orleans escapes
Result: “Plan 2050” Cost: 14 billion “prohibitive”
2000 – 2005: little money allocated to Plan 2050;
significant funds diverted to Iraq war; ACE
remediation/restoration budget slashed
Other Contributing Factors
Global warming well underway (but debate
about causes continues)
2000: US refuses to sign Kyoto Accord
Wetlands “redefined” at times to allow more
development (i.e. more habitat destruction )
Atlantic Ocean and Gulf of Mexico waters
extremely warm
Two fold increase in category 4 and 5 hurricanes
in last 30 years
Katrina Strikes!
 Flooding
in New Orleans and Surrounding
 Further
Erosion of Marshes and Wetlands
 Destruction
of Barrier Islands
Levee Breach: Katrina
New Orleans Levees
Katrina Flood
Further Destruction of Marshlands
Chandeleurs: Pre & Post Katrina
Chandeleurs: Pre & Post Katrina
End Result:
 New
Orleans, surrounding
parishes, and much of coastal
Louisiana are now even more
vulnerable to hurricanes (as
exemplified by Rita).
 Scientific American:
 “Drowning
 National
New Orleans”. October 2001
 “Gone with the Water”. October 2004