Todd

							Subsidence
      By
Todd Schneider
                 Definitions
   Subsidence is the lowering of the ground
    surface by any measurement
   Subsidence defined by John LaScola
    (1988) “The distortion of the ground
    surface that occurs when underlying
    material is removed….the change in
    elevation of any surface point…any
    caving/sinking down of a part of the
    earths crust, or lowering of strata due to
    underground excavation.”
        Most common form of
            Subsidence
   Mining of groundwater
     Areas of Subsidence due to
        Groundwater Mining
   San Joaquin Valley
   Houston-Galveston
   Las Vegas Nevada
   Southern Arizona
          San Joaquin Valley
   Nutrient rich lands
   Provides varieties of foods (apples,
    oranges, grapes, garlic, pumpkins,
    watermelons, walnuts, cherries,
    lettuce, asparagus…ect)
   Extreme agriculture has caused up to
    9 meters of subsidence.
          Houston-Galveston
   Creation of the Harris-Galveston
    coastal subsidence district (1975)
   Building of Dikes to prevent flooding
   Creation of the Fort Bend subsidence
    district (1989)
            Las Vegas, Nv
   Fasted growing city in America
   Two-thirds population in south
    central
   1907 well flowed for four years
   1938 well dried to over 3ft
    underground
   Five feet of depression between 1963
    and 1887
                Arizona
   Agriculture in the desert.
   Central Arizona Project Aqueduct
    (CAP Aqueduct) core of engineers
    project to drain water from the
    Colorado river.
         Organic soil drainage
   Soils consisting of 50% or more
    organics.
   Soils are drained for agriculture
   Building of levees along the
    Sacramento-San Joaquin delta
   Over 1,000 miles of these levees
    exist today
        Management Strategies
   Shallow flooding to slow organic soil oxidation
    and reverse subsidence through biomass
    accumulation
   Reuse dredged materials added in thin layers in
    combination with flooding
   Grow crops that use little soil and assume that it
    won’t affect the levee
   Mixing organic and mineral soils to decrease the
    amount of oxidation and continue to grow on the
    land
   Adding thick layers of dredged materials to raise
    elevation of land surface
   Creating fresh water reservoirs by deep flooding
               Conclusion
   In one way or another subsidence
    affects us all
   Millions to billions are spent on
    subsidence related activities each
    year
   There is no common solution