2010 thorsten schuetze rhine delta & planning and design with water
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    2010 thorsten schuetze rhine delta & planning and design with water 2010 thorsten schuetze rhine delta & planning and design with water Presentation Transcript

    • 10/12/10
 Structure of the lecture •  The global situation •  Hollands Struggle Against The Water •  Development of land use •  Urbanization, Infrastructure and Demography Rhine Delta - Principles for planning •  Climate Conditions and Water Availability and design with water •  Water and Water Supply Policy •  Environmental Issues and Challenges •  Planning and design with water October 12, October 12,1 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2010 2010 Introduction - The Global Situation Assist. Prof. Dr.-Ing. Thorsten Schuetze Assist. Prof. Dr.-Ing. Thorsten Schuetze 1

    • 10/12/10
 Hollands Struggle Against The Water Manmade Dutch Lowlands•  Principle section of the Dutch lowlands with enlarged heights Bosch (above) – Hooimeijer et al. 2008. More Urban Water, Design and Management of Dutch Water Cities. October 12, October 12, 5 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 6 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Subsiding Soils Coastal Protection •  Expected Soil •  Floods by storm tides and extreme precipitation events, which Subsidence until 2050 occurred in the past once in 100 years, will presumably occur (werkgroep klimaatverandering more often (every 1 – 2 years) en bodemdaling 2008) October 12, October 12, 7 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 8 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2

    • 10/12/10
 Natural water management (until ~1000) Defensive water management (~1000 to ~1500) 
 •  Acceptance of the existing situation and use of areas which •  Passive draining and protection of urban areas by protective were suitable for urban development, dunes (Den Haag), hills measures, like dikes and dams, e.g. Doordrecht, Leiden & or higher ground (Dokkum, Alkmaar) or riversides Amsterdam (Zaltbommel and Arnhem)The historical Alkmaar, Burke 1965 Hooimeijer et al. 2008. More Urban Water, Design and Management of Dutch Water Cities. October 12, 9 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 10 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Offensive water management (~1500 to ~1850) Offensive water management (~1500 to ~1850) •  Active draining systems for lakes and wetlands and of •  For example extensions of Alkmaar, Leiden and Amsterdam. settlements (Fortified towns and Polder towns).1 2 3Hooimeijer Hooimeijer 11 October 12, 2010 12 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 3

    • 10/12/10
 Offensive water management (~1500 to ~1850) Manipulative water management (from ~1850) •  Large scale urban expansions with water systems independent from polders, including, e.g. active draining and lowering of the groundwater levels. •  The Water Project for Rotterdam (1842 & 1854, Rose & Zocher)Dutch drainage areasin Europe Haartsen et al. 1989 Municipal Archive Rotterdam in Hooimeijer et al. 200813 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 14 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Schiphol Airport October 12, October 12,15 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 16 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 4

    • 10/12/10
 Development of Land use Development of Land use •  Build Up Area •  Build Up Area •  Industry •  Industry •  Glass Houses •  Glass Houses •  Parks/ Recreation •  Parks/ Recreation •  Farmland •  Farmland •  Forest •  Forest •  New Nature Areas •  New Nature Areas •  Scrub •  Scrub •  Sand •  Sand •  Dunes •  Dunes •  Freshwater •  Freshwater17 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 18 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Development of Land use Development of Land use •  Build Up Area •  Build Up Area •  Industry •  Industry •  Glass Houses •  Glass Houses •  Parks/ Recreation •  Parks/ Recreation •  Farmland •  Farmland •  Forest •  Forest •  New Nature Areas •  New Nature Areas •  Scrub •  Scrub •  Sand •  Sand •  Dunes •  Dunes •  Freshwater •  Freshwater19 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 20 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 5

    • 10/12/10
 Development of Land use Development of Land use •  Build Up Area •  Build Up Area (13,6%) •  Industry •  Industry (2,6%) •  Glass Houses •  Glass Houses (0,5%) •  Parks/ Recreation •  Parks/ Recreation (3,4%) •  Farmland •  Farmland (49,4% / arable land: •  Forest 21.96%, permanent crops: 0.77%) •  New Nature Areas •  Forest (9,8%) •  Scrub •  New Nature Areas (6,4%) •  Sand •  Scrub (3,6%) •  Dunes •  Sand (0,7%) •  Freshwater •  Dunes (0,8%) •  Freshwater (9,2%)21 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 22 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten SchuetzeAgriculture: Living and Working:23 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 24 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 6

    • 10/12/10
 Urbanization DemographyUrbanization:•  urban population: 82% of total population (2008)•  rate of urbanization: 0.9% annual (2005 - 2010 est.)25 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 26 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Demography DemographyDevelopment:•  Population: 16.485.787 inhabitants•  Area: 41.526 km2•  Density: 397 p./km2•  2038: the size of the population may have reached its peak (17.5 million) October 12,27 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 28 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2010 7

    • 10/12/10
 Demography Climate Conditions and Water Availability •  Averaged monthly rainfall and precipitation in millimetres (1971 – 2000) over the period of one year in the Netherlands (HL 5 = 15 stations). •  Precipitation: 754 mm •  Potential Evaporation: 563 mm October 12,29 Assist. Prof. Dr.-Ing. Thorsten Schuetze 30 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2010 Climate Conditions and Water Availability Climate Conditions and Water Availability •  The summer water deficit is in more than 50% of the years exceeding the average value of 122 mm (blue line). •  In 45% of the years it is up to approx. 280 mm, •  In 5% of the years it is even exceeding this height. (green line)31 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 32 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 8

    • 10/12/10
 Extreme Years Extreme Precipitation Events•  1998: 1240 mm •  Causing flood events in rivers, cities and polders•  2003: 613 mm •  Lack of retention is leading to bottleneck situations in city drainage and pumping systems as well polders and canals and rivers Egmond at the Sea in 2006 (157 mm in 25 days instead of 60 mm, source: De Volkskrant) – Ijssel near Deventer, flood, spring 199533 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 34 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Climate change – extreme precipitation Climate change – extreme precipitation•  The standard drainage capacity in the Netherlands is calculated to remove 14 mm rainfall per 24 hours. •  In September 1998 in some areas 130 mm fell in 24 hours•  In the following years comparable scenarios occurred in different regions of the country, causing damages in range of several billion Euros in rural and urban areas. Vlies, 2006 35 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 36 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 9

    • 10/12/10
 Climate change – low flows and drought Climate change – low flows and drought •  The rising sea level and more •  Causing water quality and quantity problems frequent low river discharges •  Manifold effects on eco– and infrastructure systems during the summer will allow the salty sea water to flow further inland. •  The salination of the river water will cause problems for the freshwater supply for drinking and regional agriculture. •  Especially in case of salination of the Hollandsche IJssel, the Haringvliet and the Spui.Collapsed dike near Wilnis, Ronde Venen, summer 1995 Rhine, summer 1995 Rijkswaterstaat, 2007 37 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 38 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Climate change – water stress Water Pollution •  Discharges of sewage (e.g. sewer overflows) and by agriculture are effecting freshwater bodies and coastal areas •  A visible effect is the increasing growth of algae, even though protective measures are implemented October 12, 39 Assist. Prof. Dr.-Ing. Thorsten Schuetze 40 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2010 10

    • 10/12/10
 Water Pollution Sanitation Crisis •  Every month, water-related diseases kill more than 250,000 individuals (1 individual every 10 seconds, or 1 plane crash every hour) •  More than 1.1 billion people worldwide, or one-sixth of the global population, do not have access to safe drinking water, and •  nearly 2.6 billion lack access to basic sanitation, according to the World Health Organization October 12,41 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Assist. Prof. Dr.-Ing. Thorsten Schuetze [www2.gtz.de] Assist. Prof. Dr.-Ing. Thorsten Schuetze Assist. Prof. Dr.-Ing. Thorsten Schuetze 11

    • 10/12/10
 Flevoland, Lelystad Markermeer and Ijsselmeer Assist. Prof. Dr.-Ing. Thorsten Schuetze 46 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Conventional Water Management Fresh surface water •  Fixed water levels in cities •  73% of the fresh surface water and polders include flood in the Netherlands originates risks and require: from the Rhine (approx. 65%) •  Water discharge during the and the Meuse (approx. 8%). winter and heavy The remaining 27% are precipitation events originating from smaller rivers •  Water supply during dry and from precipitation. seasons •  The water use is water supply (for drinking water, agriculture, industry and cooling water) as well as for transport (shipping) and recreation. Middelkoop, 199947 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 48 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 12

    • 10/12/10
 Water Resources & Withdrawal Groundwater•  Total renewable water resources: 89.7 cu km (2005) •  Abstracted may only be the amount of total yearly groundwaterTotal Freshwater withdrawal: recharge, which is•  8.86 cu km/yr exceeding the demand•  Domestic: 6% of connected•  Industrial: 60% ecosystems, like•  Agricultural: 34% surface water bodies or terrestrial systems (e.g.•  per capita: 544 m3/yr (2001) forests or wetlands) Middelkoop, 1999 UNEP, 200449 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 50 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Water Import Dependence Water and Water Supply Policy•  The ratio between the water footprint of a countrys imports and its total water footprint yields. •  The total drinking water produced in the Netherlands origins•  (Beef 1/13500, Soybean 1/2750, Rice 1/1400, Milk 1/790) to approx. 60% from groundwater and 40% of surface water. •  High population densities and intensive farming practices cause a continuing increase of pollution and potentially hazardous substances in fresh water resources. •  15 – 20% of the delivery costs for drinking water are often spent for the tracing and treatment of pesticides. •  Collected river water is purified by sedimentation, aeration and the adding of iron-sulphur (elimination of phosphate), before it is either infiltrated in dunes for artificial groundwater recharge or stored in lakes. Selected Countries, 1997-2001, Chapagain and Hoekstra, Water International, March 2008 / World Water Council51 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 52 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 13

    • 10/12/10
 Drinking Water from river water Responsibilities•  Nature-orientated purification by the “river-dune” or “river- The Waterworks, represented in the Association of Dutch lake” method (100 days holding time) Water Companies (VEWIN), are responsible for•  Further treatment in form of: –  the supply and quality of drinking water –  the management and•  softening in a reactor, –  the quality of all pipes up to the home water meter•  treatment with activated carbon (for the elimination of pesticides and a better taste) and finally •  The European legislation is leading for the National•  sand filtration Government (creates the legal conditions for the waterworks in form of the ‘Water Supply Act’ and the corresponding ‘Decree on the Water Supply’). •  The Provincial Government is responsible for the Duinwaterbedrijf Zuid Holland, 2008 regulation.53 Assist. Prof. Dr.-Ing. Thorsten Schuetze 54 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Responsibilities National Water Supply Priority Series The Water Boards (District Water Control Boards) together •  The National Water Supply Priority Series determines the with the department of Public Works and Water distribution of fresh water in state-managed waters around the Management are responsible for country in periods of water shortage. –  the quality and quantity of regional water. •  It applies to all areas to which the state-managed water can The Water Boards be supplied. –  control the quality of surface waters –  monitor the physical water levels, •  The remaining areas are governed by regional priority –  discharge water if necessary series, which are generally based on the national series. –  physically maintain waterways and canals. The water boards are organized in the Association of Dutch •  The series gives different priorities to four categories. Water Boards.55 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 56 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 14

    • 10/12/10
 National Water Supply Priority Series Good Ecological & Chemical Status •  The EU WFD provides a framework for the integrated management of groundwater and surface water for the first time at European level. •  For all surface waters general requirement for ecological protection, and a general minimum chemical standard were introduced, which are defining the two elements "good ecological status” and "good chemical status". •  A good ecological status is defined in terms of the quality of the biological community, the hydrological characteristics and the chemical characteristics. October 12,57 Assist. Prof. Dr.-Ing. Thorsten Schuetze 58 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2010 Competition of ecology and other uses Competition of ecology and other uses•  Set of uses, like essential drinking •  Navigation and power generation is also adversely affecting water supply and flood the status of water, but these activities are open to alternative protection, can adversely affect approaches. Derogations for those cases are subject to the the status of water. exclusion of alternatives because they •  are technically impossible,•  Derogations from the EWFD •  are prohibitively expensive, requirement are provided to •  produce a worse overall environmental result. achieve good status for these cases, as long as all appropriate mitigation measures are taken. Rijkswaterstaat, 2007 Rijkswaterstaat, 200759 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 60 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 15

    • 10/12/10
 Environmental Issues and Challenges Resource Flows Environmental Issues and Challenges61 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 62 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Upward Seepage, Salinization and Salt Water Intrusion Resource Flows and Pollution Nord Holland: Nes an de Amstel and Amsterdam (Background) Highway at Schiphol Airport63 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 64 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 16

    • 10/12/10
 Biodiversity and Natural Water Balance Energy and Food Production Flevoland: Vivijertocht, A6, Ijsselmeerdijk, Windmills & Conventional Power Plant Nord Holland: Zaandam, Watering, A8, Reef & Jagerplas65 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 66 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Biodiversity and Natural Water Balance Nord Holland: Bovenkerk, Amstelveen, Amsterdamse Bos & De Poel October 12,67 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 68 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2010 17

    • 10/12/10
 Coastal Protection – Dikes and Dunes Coastal Protection – Dikes and Dunes•  Building higher dikes? •  Adapted Solutions for different locations•  Using natural processes including water and wind? Nieuwe Maas, storm surge barrier [Flood 1953] “Strengthening” of coastline with dunes and designated flooding areas October 12, October 12,69 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 70 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Coastal Protection – Dikes and Dunes River flood – dikes and floodplains•  4 scenarios dune expansion & sand motor for the Delftland •  1995,‘deltaplan’ for the rivers - debate dikes and floodplains (reference to the gigantic dune in Arcachon, France) •  Finally priority was given to SPACE FOR THE RIVERS. traditional Loire model Mississippi model October 12, October 12,71 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 72 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 18

    • 10/12/10
 River flood – dikes and floodplains River flood – dikes and floodplains •  Particularly “bottleneck” areas ask for by-passes •  By-passes can be created by “green rivers” or “blue rivers”Arnhem 1830 Arnhem 2000 October 12, October 12, 73 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 74 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze River flood – dikes and floodplains River flood – dikes and floodplains •  Combination with multiple uses, such as residential, nature and •  Competitions with visionary design proposal stimulate the recreation can increase public support and economical feasibility. discussionIjssel bypass near Kampen October 12, October 12, 75 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 76 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 19

    • 10/12/10
 Building in deep polders Building in deep polders•  Intensive agriculture and conventional water management •  Development of the Zuidplaspolder according to local basic contributes to subsiding soils, particularly in low lying polders conditions, including topography, soil quality and seepage•  How to develop low lying polders in future? •  Integration of appropriate program for development (land use) October 12, October 12,77 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 78 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Building in deep polders Building in deep polders•  Safety through flood protection (from river & the see – barriers •  Water storage against drought, flood and upward seepage in Maasland and Krimpen)•  Dike collapse can only lead to limited flooding of 1.3m max. (designated flooding area) s l se ia ou nt sh ide re s s tu gla re na October 12, October 12,79 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 80 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 20

    • 10/12/10
 General principles Sustainable Water Management•  Careful analysis and understanding of the location and the natural and anthropogenic basic conditions (SWOT analysis •  Sustainable urban water management is including the regarding climate, topography, infrastructures, etc.) different sections of the urban water cycle:•  Differentiation between outer- and inner dike areas. •  water supply & distribution •  water use & saving•  Multiple use of space and functions for the creation of •  Water reuse and recycling synergies between different sectors (agriculture, nature, urban, •  water storage and augmentation etc.)•  Consideration of Resource management principles, particularly Integrated Water Resource Management principles EUWFD (water quality and quantity issues) Schuetze et al. UNEP IETC DTIE & TU DELFT, (2008) Every Drop Counts, Environmental Sound Technologies for water use efficiency in the urban and domestic environment. October 12, October 12,81 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 82 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Rainwater Management Sustainable Urban Rainwater Management in general consists of different modules which can be summarized to the following main topics which are interacting: •  rainwater retention and purification (e.g. by soil and sand on green roofs or in tanks and basins, lakes and open water systems), •  rainwater infiltration (on surfaces like unsealed traffic areas, in swales, infiltration ditches or infiltration wells) •  rainwater evaporation (by open water surfaces and plants, e.g. lakes, green roofs, gardens or lawn areas), •  rainwater harvesting (from roofs or open spaces like pavements courtyards and parking lots and roads) •  rainwater utilisation (for cleaning, toilet flushing, garden watering) October 12,83 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Assist. Prof. Dr.-Ing. Thorsten Schuetze 21

    • 10/12/10
 •  Rainwater collection and utilization •  in many countries allowed for service water purpose •  Possible drinking water source in areas with polluted fresh water resources (e.g. Arsenic, Fluor, Tin, etc.) Assist. Prof. Dr.-Ing. Thorsten Schuetze Assist. Prof. Dr.-Ing. Thorsten Schuetze Supportive regulations for rainwater utilization Supportive regulations for rainwater utilization•  In Belgium, all new buildings (with roofs bigger than 75m2) have to be equipped with rainwater harvesting and utilization facilities! (building code by the Ministry of Environment - Vlarem II (art. 6.2.2.1.2.).•  The rainwater systems has to be: –  1. collected and utilized –  2. infiltrated on the own property –  3. retention and discharge in natural or artificial surface water bodies –  4. discharge in the rainwater sewer in the street (1. is not obligate for existing buildings, however 2., 3. and 4. have to be applied as much as possible)87 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 88 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 22

    • 10/12/10
 Supportive regulations for rainwater management Guiding principles•  In the Netherlands the three-step strategy is the basic •  Priority for the decentralised management of rainwater, guiding model, which has been introduced in the Netherlands particularly in new urban developments in the Netherlands for the decentralized management of rainwater (however it by the three step strategy (WB 21): doesn’t support utilization of rainwater). 1.  Collection 2.  Retention•  developed by the Dutch Advisory Committee on Water 3.  Discharge Management in the 21st Century in 2001, to ensure safety and reduce water related problems in the 21st century. The aims of the strategy are: –  the creation of seasonal water storage to cope with drought and –  the decentralized retention of rainwater during heavy rainfall. October 12, October 12,89 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 90 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze Guiding principles Fluctuation Model •  Peak & Seasonal Storage of Rainwater requires •  Seasonal and peak storage of rainwater requires retention volumes which can be provided by technical or fluctuation in water levels due to seasonal variations in natural sound means. (Some water boards ask for 10% evaporation and precipitation. open water surface areas). •  Differentiation between open surface water bodies with different properties. •  Closed surface water systems in polders (lakes, ditches and canals, which can combined to circulation systems and allow the fluctuation of water levels (peak and seasonal) as well as keeping / enhancing the water quality. •  Rivers and streams which are flowing based on natural slope Nijhuis 2007 October 12,91 Assist. Prof. Dr.-Ing. Thorsten Schuetze 92 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2010 23

    • 10/12/10
 Fluctuation Model •  Required fluctuation of water Thank you for your attention level is dependent on the available water area in relation to catchment area Examples for design with water will be •  100% water area requires presented next week approx. 18 cm fluctuation •  25% water area requires approx. 72 cm fluctuation •  10% water area requires approx. 180 cm fluctuation (simplified model)Nijhuis 2007 October 12, 93 October 12, 2010 Assist. Prof. Dr.-Ing. Thorsten Schuetze 94 Assist. Prof. Dr.-Ing. Thorsten Schuetze 2010 24