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An example of a metropolitan delta is situated in The Netherlands: the city of Rotterdam and its surrounding area….. Click to start this lecture in pictures on hydrological problems and solutions Note: the scale of the pictures is indicative of the problems, and is not necessarily accurate Ondergrond Nederland uit de Vijfde Nota Ruimtelijke Ordening, 2001, Min VROM, Bronnen: MUST – Geosys (Frankrijk) – Bosatlas – Nationaal Geografisch Instituut (België), Institut für Angewandte Geodäsie (Duitsland) - ministerie V&W, directie Noordzee en Meetkundige Dienst – NEO
drinking water to the city drinking water to the city Problem: Extraction of drinking water from the dunes is hamperedbecause of more salt intrusiondue to the rise in sea level Impacts:Salinisation of drinking water and decline of the ecology of the inner dune belt Solution: Stop water extraction: use rain and/or river water reservoirs for drinking water This will restore the high water table in the dunes, and will enlarge the fresh water lens, thus recovering the upward seepage in the inner dunes which restores the dune ecology pumping station 1 fresh water salt water
drinking water reservoir drinking water drinking water Solution: a: pump air through a perforated pipe on the river bed, generating an upward water flow and/or:b: allocate inlet points for drinking water further upstream c: and/or create a drinking water reservoir Problem:rise in sea level causing further intrusion of salt water into the river Impact: increasing salt content of drinking water from river drinking water reservoir 2
Problems: Pesticidepollution of surface water andlowering of groundwater table in inner dunes due to bulb cultivation Impacts: Deterioration of aquatic ecosystems and decline in quality of terrestrial ecosystems in the inner dunes Solution: Re-allocate bulb cultivation to less vulnerable sites and construct a fresh water basin. Then upward seepage of fresh water and the water table in the dunes will restore. 3 fresh water salt water
Problems: a: rise in sea level causing salt in groundwater b: water pollution from glass house horticulture Impacts: Water for irrigation needs desalinization and purification Solution: use closed water chain within sealed unit horticulture 4 fresh water salt and polluted ground- water salt water
Problem:rise in sea level causing coastal zone erosion Impact: risk of flooding of western part of The Netherlands Solution: construct a dam along the coast 5
Plan Lievense:wind turbines also provide energy for filling the reservoir 6 high tide low tide Problem: oil pollution and sea rising Impacts: death of sea birds and marine organisms Solution: implement “green” sources of energy, e.g. wind and tidal, using the coast as an energy zone in combination with protection against flooding by the sea
Plan Lievense:wind turbines also provide energy for filling the reservoir Problem: oil pollution and sea rising Impacts: death of sea birds and marine organisms 6 high tide low tide Solution: implement “green” sources of energy, e.g. wind and tidal, using the coast as an energy zone in combination with protection against flooding by the sea
Problems:drainage in agricultural land causes seepagefrom wetland to agricultural area combined with lower river level causes water loss in summer Impacts:lowering of groundwater table, causing decline in quality of wetlands 7 Seepage to river seepage Seapage Seapage Solutions: a: cease agriculture, increase wetland area and/or create housing on water b: increase river level in summer by reservoir management upstream and construction of locks
seepage seepage seepage from the river seepage from sea Problems: a: rise in sea levelb: higher peak levels of rivers c: lowering of groundwater table due to drainage of pastures Impacts: a: land decline through mineralization of peat soils b: more seepage from rivers, requiring more pumping (drainage) c: more seepage of salt into groundwater, requiring more pumping d: damage to building foundation due to land level decline 8 Solutions: a: cease agriculture and choose other forms of land use which allow seasonal variation in water level and salt content of water (e.g. wetlands) b: combine this with the creation of wider flood plains, thus lowering the peak river levelsc: modify building techniques: e.g. place buildings on pillars or on floating islands
Problem:Higher peak water levels of the river due to embankmentof flood plains upstream and increased precipitation Impacts:risk of overflow of river banks causing flooding of the enclosed areas 9 Solution: a: hold water upstream, through modified land use and reservoir construction b: create wider flood plains (with flooding housing) c: construct roads along the rivers on pillars
Solution: increase discharge in summer by: reservoir management upstream and/or construction of locks Problems:a: lower water discharge in summer b: increased salt concentration in summer c: worse water qualityImpacts:a: problems with shipping channels b: insufficient water supply for agriculturec: decline in quality of aquatic ecosystems 10
Problems:bad water quality causedby sewage overflow from the city during more extreme rainfall eventsImpacts:water less suitable forrecreation and more health risks Solution: prevent overflow of sewage by: separating rain water and sewage systems and construction of underground reservoirs for retention of sewage recreational area 11
Zoom out 12 Problem:climate change causes sea level rise and increased precipitation. The latter in conjunction with other factors, e.g. the reduction in the extent of flood plains through embankment leads to higher peak water levels in rivers;Impacts:higher risk of flooding (by sea and rivers), salinization of drinking water and potential water pollution, e.g. by flooding of off shore oil platforms and by oil transport.
tidal lake flood plain 12 drinking water reservoir storm surge barrier Problems:sea level rise and higher peak river levelsImpacts:higher risk of flooding and potential pollution Solutions: a: create wider flood plains b: construct a retaining dam and a storm surge barrier c: reduce risk of pollution by implementing wind- & tidal energy and construct a reservoir for drinking water