Summary The Living Environment ENVS1017 Module 2

MODULE 2: THE COASTAL ENVIRONEMNT

Lecture 9, Week 5
WETLANDS AND ESTUARIES

LECTURE OUTLINE:
• Importance of wetlands and estuaries
• Estuary zones
• Estuary classification
- Wave-dominated
- Tide-dominated
• Tidal zonation
• Estuary habitat
- Mangroves
- Salt marsh
• Estuary hydrodynamics
- Stratification and mixing
- Tidal range inside estuaries
- Tidal asymmetry
- Tidal prism and fishing times

CATCHMENT FRAMED APPROACHES TO ENVIRONMENTAL MANAGEMENT
• Treat catchments as integrated networks of flows and fluxes
• Treat causes not symptoms of problems in catchments
• Work within an ecosystem based or nature based approach


WETLANDS
• Wetlands = periodically or continuously inundated areas with shallow water and or
saturated soils
• Have plants and other biota that are adapted to wet conditions
• Occupy an intermediate position between terrestrial and fully aquatic ecosystems
• Fulfil important hydrological and biochemical functions
• Possess a diverse range of geomorphic and sedimentary features
• Support high biodiversity

ESTUARIES
• Estuaries = a semi-enclosed coastal body of water, with a free connection to the open sea,
and within which sea water is diluted with freshwater from land drainage
• In other words: the seaward limit of a drowned valley which receives sediment from both
river and marine sources and their morphology is influenced by tide, wave and river
processes

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,WHY ARE ESTUARIES IMPORTANT?
• Provide a range of habitats: mud flats, sand flats, salt marsh, mangroves, wetlands
• Estuarine habitats (e.g. salt marsh) can filter water of pollutants
• Important nurseries (e.g. for fish and shellfish, provide protection)
• Buffer zones: shore stabilisation and coastal protection e.g. from storm surges
• Support lots of human populations
• Hugely important for economies, recreations and culture

ADDITIONAL PROBLEMS FOR ESTUARIES
• Estuarine habitat loss due to historic draining and infilling e.g. to farmland
• Often low-lying developments e.g. Tuggerah Lakes, Central coast
• Eutrophication due to high nutrient loads
• Pathogens and pollution e.g. from runoff
• Decline of sea grass, salt marsh and mangroves
- In NZ mangrove spread is occurring

HEALTH OF AUSTRALIAN ESTURIES




ESTUARY ZONATION
• Most estuaries have 3 main zones:
- Inner river dominated
- Central mixed
- Outer marine dominated (waves and tides)
• Different parts of the estuary have different energy regimes




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,ESTUARY ZONATION




ESTUARY CLASSIFICATION
• The physical properties of estuaries depends on: geology, waves and tides, and amount of
available sediment
• Classification considering morphology and dominant processes
- Two main types are:
o Wave dominated estuaries
o Tide dominated estuaries

ESTUARY CLASSIFICATION: WAVE DOMINATED ESTUARY
• Coastal bedrock embayment that has been partially infilled by sediment derived from both
the catchment and marine sources, in which waves are the dominant force shaping the
gross geomorphology
- E.g. Tuggerah lakes (NSW), Broke Inlet (WA)




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, WAVE DOMINATED ESTUARY




• Energy distribution
- In outer zone waves break and only a little tidal energy comes in through the inlet
• Plan view of morphology
- Barrier system and tidal inlet
- Ebb and flood tidal delta
• Profile of sediments
- Coarser sediments in outer and inner zones
- Note flood tidal and bay head deltas
- Fine sediments in central zone


ESTUARY CLASSIFICATION: TIDE DOMINATED ESTUARY
• Landward tapering funnel shaped valley, bounded by various intertidal sedimentary
environments such as intertidal flats, mangroves, saltmarshes and saltflats
- E.g. Fitzroy river (Qld), Victoria river (NT)




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