Thursday, March 18th, 1999

Announcements: none

Lecture notes:

I. Preview
    A. Mississippi Water Shed
            1. Enormous
            2. Heavily populated
            3. Diverse

    B. Floods, on average, are higher than they were 100 years ago

II. Louisiana (New Orleans)
    A. Criss-crossed by tons of little rivers

    B. Consists of the Mississippi River, Red River, Black River, Old River, and the Atchafalaya River

    C. Several deltas formed from the Mississippi River all over Southeastern Louisiana (Birdfoot Delta)

    D.  A schematic river

    E. Every 1,000-2,000 years the Mississippi River needs to change its delta area

    F. Crevasse splays--cracks, holes in the wall of the river that forms; break in the natural levy wall; ones near the
        Mississippi River in Louisiana (Birdfoot) were caused by floods

III. New Orleans
    A. City is below the river level

    B. Any serious crevasse splays near or at New Orleans would wipe out the entire city

    C. Levies rose because when the water goes over the levy, the levy tends to increase in size

IV. Mississippi River
    A. When the bend (Trumball's Bend) in Mississippi River  was "cutoff" and left an oxbow lake and formed Old River;
        the Atchafalaya

    B. Therefore, the amount of water was 30% less going into the Mississippi River and rather into the Atchafalaya River

    C. This allows more salt water to come into New Orleans because the fresh water usually pushes out the salt water in
        New Orleans

V. "Great Flood"
    A. 153 days of flood water readings (over flood stage)

    B. Average of over 30 feet of water in areas of flooding

    C. New Orleans got barely or no flooding because they made an artificial crevasse splay beyond New Orleans got
        barely or no flooding because New Orleans made an artificial crevasse splay beyond New Orleans (south of the
        city)
 
    D. The water then had an easier time flowing and flooding out areas south of New Orleans

    E. The Atchafalaya also helped stop the flooding of New Orleans