Urban Flood Management in Dordrecht

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The municipality of Dordrecht is partner in the international UFM (Urban Flood Management) project, together with Hamburg and London (Herk, 2007). The objective of the project is to adjust spatial designs to deal with a possible flood. As the

Fig. 7.6 Increase of the flexibility of the urban water system and extraordinary buildings (Source: Baca Architects, London, 2007)
Fig. 7.7 New building locations in the Thames gateway (Source: Baca Architects, London, 2007)

Dordrecht pilot the project Stadswerven was chosen, a revitalising project next to the inner city.

In the project the probability of a flood is compared with the effects of a flood. If the probability can be decreased by a better protection, the effects - damage and casualties - will increase in case of a flood (Fig. 7.12). Wouldn't it be more desirable to accept that certain areas will flood if, in that case, the effects could be minimised? The urban areas can be laid out in a flood-proof way and measures could be taken in order to make the effects of a flood acceptable. The decision to accommodate floods in urban areas becomes a building block in the design process. The closure of the city with a mountain high wall leads to a completely different design assignment than an interwoven city with water

The project improves climate proofing at two levels: the Master plan and the individual building (Fig. 7.13). In order to do so, the flood itself as well as the possible damage is modelled and used as input in the design for the neighbourhood and buildings. The design is adjusted if measures decrease the chance of a flood and increase the flexibility of the area.

Fig. 7.8 Dikes enforce the water to be pushed upstream (Source: Baca Architects, London, 2007)
Fig. 7.9 Proposal for an alternative flood defence (Source: Baca Architects, London, 2007)

In the Master plan the flood strategy is introduced (Baca Architects, 2007), in which water - if apparent in large amounts - is used as a temporary quality in the urban design. By giving water a role in the city it becomes an archipelago (Fig. 7.14). The new 'inlets' for water are combined with parks, recreation and artificial flood plains (Fig. 7.15).

Fig. 7.10 Lifted building (Source: Baca Architects, London, 2007)
Proyecto Con Piezas Ensamble
Fig. 7.11 Urban design (Source: Baca Architects, London, 2007)
Fig. 7.12 Risk classes (Source: Renn, 2002, (Klinke & Renn, 2006))
Fig. 7.13 Climate proof buildings (Source: Baca Architects, London, 2007)
Fig. l.14 Archipelago Dordrecht (Source: Baca Architects, London, 2007)
Fig. l.15 Flood strategy (Source: Baca Architects, London, 2007)

The translation to an urban design leads to different dwelling types and public space, designated by whether floods occur frequently, regularly or seldomly. The public space and the buildings are adapted to the specific situations (Fig. 7.16). On top of this, in the design, integration takes place with a sustainable energy supply, transport and socio-cultural amenities (Figs. 7.17and 7.18).

7.3.3 Zuidplaspolder

The Zuidplaspolder is one of the deepest polders in the Netherlands and contains the lowest point to be found in the country (- 6.76 m below sea level). The polder is a typical Dutch landscape. The peat is dug off and the groundwater level is kept artificially low to suit agricultural purposes. The rest of the peat oxidises and this causes a further reduction of the ground level. These problems are exacerbated by climate change. It becomes increasingly difficult and costly to pump water out of the polder. This problem is exaggerated by the changes in climate, i.e. increased winter precipitation and shortage of water in summer. An added problem is sea

Visual Ideas bciCCI

expedient flood recovery Hard surfaces near water Soft surfaces inland expedient flood recovery Hard surfaces near water Soft surfaces inland

Floating Reactive Properties Reactive Properties Water Channel

Properties Sliding retreating used for building properties for extreme and recreation flood events

Fig. 7.16 Spatial proposal for a flood typology (Source: Baca Architects, London, 2007)

Floating Reactive Properties Reactive Properties Water Channel

Properties Sliding retreating used for building properties for extreme and recreation flood events

Fig. 7.16 Spatial proposal for a flood typology (Source: Baca Architects, London, 2007)

Integrated development features

House Types LMng Bridge Office A Cukunl Hob Green Wheel» Ne.thbourtvcxxl Commercial Dutrict Heatinj Natural Waste

Live/Work TW«. Sport. Hub A District Renewable» A Power from Water Treatment

TrKW^LfW* Power Centre Waste

Integrated development features

House Types LMng Bridge Office A Cukunl Hob Green Wheel» Ne.thbourtvcxxl Commercial Dutrict Heatinj Natural Waste

Live/Work TW«. Sport. Hub A District Renewable» A Power from Water Treatment

TrKW^LfW* Power Centre Waste

Fig. 7.17 Integrated proposal (Source: Baca Architects, London, 2007)

level rise, which increases saline seepage through the ground, which leads to saline groundwater (Fig. 7.19).

For the polder, a Master plan has been developed (Fig. 7.20), where in the ten years from 2010 between 15,000 and 30,000 new houses are intended to be built, 125 ha of business space, 280 ha of greenhouses will also be developed and 500 ha of nature will be realised. The question is how to realise all this in a climate-proof

Fig. 7.18 Visualisation of the plan (Source: Baca Architects, London, 2007)
Fig. 7.19 Depth of the Zuidplaspolder (Source: Provincie Zuid-Holland)

manner. Therefore, Zuidplaspolder is given the special status of a hotspot in the 'climate changes spatial planning' program (www.klimaatvoorruimte.nl).

The hotspot project consists of three phases. In the first phase research is conducted on the changing conditions due to climate change and looking specifically at repetitive times of water annoyance. The possible changes in land use are mapped, using the spatial scanner (Schotten et al., 1997). This results in the envisioning of future perspectives. These perspectives are translated into design challenges in the second phase of the hotspot. Design research provides the challenges with solutions, making use of the back casting method, in which the most extreme expected future changes form the input for design at all levels, from building to region. The first area is designed climate proof (Fig. 7.21). In the third phase a costs benefits analyses is

Fig. 7.20 Masterplan Zuidplaspolder (Source: Pelt et al., 2006)
Fig. 7.21 First climate proof design (Source: Xplorelab, provincie Zuid-Holland, 2007)

carried out and finally, the climate proof quality of Zuidplaspolder is laid down in a covenant signed by all the partners involved.

7.3.4 Building with Water in Haarlemmermeer

Haarlemmermeer is an area under pressure of several spatial claims. The low lying polder is almost the lowest part of Randstad Holland, where all water is collected naturally and needs to be pumped out again. Moreover, the soil is compacted, which causes the lowering of the ground level. Salinity strikes hard during the shortage of precipitation in summer. The changes in climate urge for substantially more water to be stored, while the existing spatial claims of housing, urban developments, noise barriers, the safeguard contours of Schiphol airport, nature and landscape does not all fit in the space available. If all spatial claims were added up the polder is circa 15% too small. There is not enough money to realise green space and nature, the existing building techniques have a negative impact on water, salination and compacting of the soil. Yet, a sustainable water system, ready to meet the challenges of climate change, requires more space (Kuypers, 2007).

The task is to design an innovative landscape, where green, red and blue functions can be combined. Only then can spatial wins be realised. The plan is developed from three points of view: Controlscape, Mindscape and Landscape.

Technical research is conducted on market developments and water. This research is part of Controlscape. The research topics are the storage of water in extreme situations, dealing with safety and dynamics, the details of slopes and the natural circulation. The market study answers questions about target groups, the things to which they are attracted and if a competitive offer can be developed.

Mindscape focuses on the involvement of stakeholders, the feasibility, organisation and finance. The aim is to create a structure and cooperation, based on trust, for the long term. Landscape focuses on the integral design for the area (Fig. 7.22).

Green and blue structures steer the spatial plan. The houses are projected at the edges where land and water meet. The designed framework offers possibilities for

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Fig. 7.22 Integral design for the pilot location (Source: Kuypers, 2007; © PPP Bouwen met water (www.bouwenmetwater.nl))

high and low densities. The infrastructure and space for parking is reduced to a minimum. The only way to reach the islands is by boats. The market risk is spread out because of the flexible phasing, in time as well as in space. The net spatial win is around 15% - surface water even 50%. The storage capacity in the design is enlarged in order to store more rainwater. The financial return in this plan is 15% higher than in comparable plans, even without counting in the profit in water management.

7.4 Heat in the City

In the last century 38 heat waves have been recorded of which 11 occurred after 1990 and 6 after 2000. A heat wave is in the Netherlands defined as a period with minimal 5 consecutive days above 25°, of which three above 30° (KvR, 2007). It is expected that heat waves will occur more often in the future (IPCC, 2007). Due to the rise in temperature, due to Global Warming, the average temperature in 2050 is predicted to equal the temperatures during the heat wave in 2003 (Fig. 7.23). This heat wave is one of the most extreme last century and many mortalities were recorded throughout Europe. During the two heat waves in 2003 several hundreds of deaths were recorded in the Netherlands. Robine (Robine et al., 2007) states that the number of mortalities in Europa reached 80,000. In cities the effects were especially severe. Vulnerable people, like the elderly (Fig. 7.24), people with heart diseases and breathing problems were harmed the most. Under the deaths only a small number could be explained by the so-called harvest effect (Pirard et al., 2005). The harvest effect means that people die a few months earlier then they would have naturally.

Fig. 7.23 In 2050 the average temperature equals the temperature during the heat wave in 2003 (Source: Nickson, 2007; © Greater London Authority)

Vulnerability to heat

Fig. 7.24 Sensitivity of elderly for a heat wave (Source: Nickson, 2007; © Greater London Authority)

Temperature distribution in London. August 2003

Temperature distribution in London. August 2003

Fig. 7.25 London in red, temperature during the heat wave of August 2003 (Source: Nickson, 2007, © Greater London Authority)

The effect of a heat wave is greater in the city than in the countryside, because cities heat up faster, due to the large amount of stone and pavement. During the night the temperature stays high. In an urban area like London the temperature can be 8-10° higher than the surrounding countryside (Fig. 7.25). This is called the Urban Heat Island effect (UHI). The city needs to be adjusted to minimise the effects of heat waves in order to prevent the population from buying air-conditioning units, which use large amounts of energy and thus exacerbate the climate problem.

Adaptation of the city and buildings to higher temperatures and heat extremes is very important because the following developments increase in the future:

• Urbanisation in high densities;

• Air pollution due to traffic;

• The number of air-conditionings;

• Less cooling because of droughts;

The air temperature is not the only factor that influences the heat effect in the city. The long and short wave radiation, humidity and wind speed also influences the experience of heat by the people. In order to weigh these aspects the PET-index (Physiological Equivalent Temperature) has been developed, which makes it possible to measure the thermic component of climate and thus the experienced comfort

Fig. 7.26 Heat stress in London, 2003 (Source: Gilbert, 2007)

by the population (Kratschner, 2007). The PET can be used as a standard for heat stress in the city (Fig. 7.26).

Several measures can be used to deal with heat stress (Based on Nickson, 2007):

1. In case of large-scale urban developments the ventilation can be improved by a smart design. For example the shape of buildings needs to be high and small preferably, but the positioning of the buildings is also important. The city may be 'greened' and the number and variation of microclimates needs to be increased to give a choice for a specific environment depending the climate and find suitable cooling. Seasonal shadow can be introduced - like parasols- or sprinklers can have a cooling effect in public space, both of which are realised temporarily. In general, it is useful to realise pavements with a cooling effect - material that absorbs heat without getting hot - and plant climate proof trees, which are able to survive during heat periods;

2. In designing buildings the first win is to save energy. The saved energy will not contribute to the heat in the city. The use of white façades - which reduce radiation - the planting of trees and the use of 'cooling' materials can reduce the heating effects of buildings as well.

3. It is diligent to create a cooling-cascade: firstly minimise heat production, secondly prevent heat from entering the building, thirdly take care of ventilation and design the heat balance inside - minimal thermal mass, high ceilings and the use of vegetation - and finally use city heating and cooling;

4. Ultimately, a emergency plan in case of heat waves must be developed, which focuses on minimising traffic, encouraging clean cars (not restricted to heat wave times only) and communicate the availability of cool buildings in the neighbourhood, where people can shelter in case of high outside air temperatures

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