1. Introduction1.1. What is an estuary? 1.2. Humanity and estuaries1.2.1. Sedimentation from sediment eroded from cleared land in the hinterland1.2.2. Overfishing and trawling1.2.3. Destruction of wetlands1.2.4. Eutrophication1.2.5. Pollution1.2.6. Dams.1.2.7. Dykes for flood protection.1.2.8. Human health risks.1.3. The future of estuaries and the quality of life of the human population living on its shores1.4. The solution1.5. Ecohydrology science: the structure of this book. 2. Estuarine water circulation 2.1. The average residence time 2.2. The age of water2.3. Exposure time vs. residence time2.4. Vertical mixing and stratification 2.5. Lateral stratification, trapping, and shear 2.6. The importance of the bathymetry on flushing2.7. The importance of flows near the river mouth on flushing2.8 The special case of lagoons3. Estuarine sediment dynamics3.1. Geomorphological time scales3.2. Sediment dynamics3.2.1. The distinction between mud, silt and sand3.2.2. Sand dynamics3.2.3. Mud dynamics3.2.4. Engineering implications3.2.5. Biological implications3.3. Net sediment budgets3.3.1. The age of estuaries3.3.2. Net erosion or progradation3.3.3. Formation of mud flats3.3.4. Formation of tidal wetlands by the vegetation colonizing bare intertidal areas3.4. The size of the mouth4. Tidal wetlands4.1. Description4.2. Hydrodynamics4.3. Wave attenuation by wetland vegetation4.4. Ecological processes within a tidal wetland4.4.1. Mangroves 4.4.2. Saltmarshes 4.4.3. Supratidal mud flats 4.5. Enhancement of estuarine fisheries productivity by ouwelling from tidal wetlands4.6. Groundwater4.6.1. Mangroves4.6.2. Saltmarshes4.7. Physics-biology links 5. Estuarine food webs 5.1. Simple food webs in clear waters5.1.1. Definitions5.1.2. Clear waters 5.2. The key role of detritus 5.3. The role of groundwater 5.4. Link to pelagic food web (fisheries) 5.5. Estuarine ecology 5.6. Over-stressed ecosystems5.7. Seagrass and coral reefs6. Ecohydrology models 6.1. Engineering models 6.2. Ecosystem models 6.2.1. Predator-prey relationship 6.2.2. Estuarine ecosystem models6.2.3. An estuarine ecohydrology model6.3. Coral reef ecohydrology model7. Ecohydrology solutions7.1. Freshwater7.2. Estuaries7.3. Coastal waters 7.4. Managing human health threats 7.5. Habitat creation 7.5.1. Saltmarshes 7.5.2. Mangroves7.5.3. Seagrass 7.5.4. Coral reefs 7.5.5. Sediment capping7.6. Protection against natural hazards 7.7. A future for estuaries and coastal waters? 8. References 9. Index