Estuaries and coastal waters need river catchment management'

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Estuaries and coastal waters need river catchment
management. Dr. Eric Wolanski, FTSE
Australian Institute of Marine Science
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(No Transcript)
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Mud is a most important pollutant particularly in
the tropics where intense rainfall facilitates
erosion. Mud -increases turbidity -degrades the
habitat -kills plankton, coral, seagrass and
benthic organisms.
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In the lower Cimanuk River (Java), since
deforestation in the highlands in WWII, the
levees now reach 3 m height.
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Effects of dams -decreasing peak
floods -decreasing sand load but often letting
mud through Usual results -In many cases (eg
Nile River delta), coastal erosion has resulted
(hundreds of m/decade) -Increased muddiness of
estuaries. -In other cases (eg Ord Estuary,
Australia), siltation of the estuary has resulted
(3 m in 30 years). all accompanied
by fisheries collapse.
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Sediment trapping capacity of salt marshes and
mangroves in coastal areas is enormous
(1,000-2,000 tonne km-2 year-1). Also, sediment
trapping and nutrient removal along the river by
natural wetlands or flood plains could also be
very significant diminishing sediment flow to the
coastal areas.