Com Coast

The ComCoast project (www.comcoast.org) aims at changing the existing dikes into a multifunctional coastal defence (Fig. 3.5). This is necessary because of climate change, sea level rise, increased wave activity and level of tides, increased pressure on the coast by human activity and coastal erosion. A multifunctional coast is more resilient for these changes and is capable of incorporating more functions. Within the Interreg-project is cooperated in eleven locations along the coasts of South East England, Belgium, the Netherlands, Germany and Denmark. In the project, managed by Rijkswaterstaat, is cooperated between the province of Zealand and Groningen, the University of Oldenburg, the Environmental Agency (UK), the Min-

VIER SCENARIO'S MOOR OE DELFLANDSE KUST

Scenario 1: " Autonoom" Net Groene Fundament = zeewoortse uitbreidmg met minimaal 500 ha. t.b.v.: - veiligheid (lange termijn) ■ natte en droge duinnatuur • groene recreatie

Scenario 2: "Randstad" Bouivt voort op Greene Fundament door trans formatier van acht erlügende glasgebieden rand N211 te ontivikkeien als hoogwaardrg groen woon- en rec rent rem i lieu georieriteerd op Den Haag en ft'dom.

Scenario 3: "de Strippen" Groene Fundament is basis voor bene leide verstedeli iking vanof W211 fontg innings basis'). Tussen de strippen brede duinzones. Gefaseerde uitbreiding zeewoorts maqeii ik door zeewaarts verschuiven afslaglijn

Scenario 4: "Kustuitbreiding" Eenmolige omvangrijke Fandaanwin-ning biedt ruimte voor grootscho-lige verstedelijking t.b.v. Rands tod. Vereist ingrijpende aanpassing van ontsluitende en verbindende infra-structuur.

Fig. 3.4 Four scenarios for the Delfland coast (Source: Bureau Nieuwe Gracht, 2005)

istry of the Flemish community (B), the Danish Coastal Authority (DK), the municipality of Hulst and the water boards Zealand islands and Zealand Flanders.

The possibilities to develop a multifunctional coastal zone can be found at land as well as seaward (Fig. 3.6).

Within the ComCoast project five different concepts are developed (Oedekerk, 2006).

The front shore defence (Fig. 3.7) consists of a construction in front of the coastline, which improves the defensive qualities of the primary defence, the dike, by decreasing the wave-activity. The area between the dike and front shore defence develops as a brackish zone with a decreased wave-action and is suitable for the development of nature, recreation and saline agriculture.

Over time this front shore defence might be developed into a permanent defence (Fig. 3.8).

Suppletion (Fig. 3.9) with sand, mud, shingle or gravel in front of the coast strengthens the natural defence and offers a valuable habitat for several species. This sedimentation zone offers chances for nature, recreation and saline agriculture. On the other hand, if a lot of sand is required to protect the coast - and due to a quick rising of the sea level this is expected -, the living ecosystem of the beach

Scenario 4: "Kustuitbreiding" Eenmolige omvangrijke Fandaanwin-ning biedt ruimte voor grootscho-lige verstedelijking t.b.v. Rands tod. Vereist ingrijpende aanpassing van ontsluitende en verbindende infra-structuur.

Fig. 3.4 Four scenarios for the Delfland coast (Source: Bureau Nieuwe Gracht, 2005)

Fig. 3.5 Change from a single dike towards a multifunctional coastal defence (Source: Comcoast, 2007b)

Fig. 3.7 Front shore defence (Source: Oedekerk, 2006)

Fig. 3.6 A land and seaward multifunctional zone (Source: DHV, 2006)

Fig. 3.7 Front shore defence (Source: Oedekerk, 2006)

Fig. 3.6 A land and seaward multifunctional zone (Source: DHV, 2006)

Fig. 3.8 In four steps towards a new closed defence (Source: ComCoast, 2007a)

Fig. 3.9 Suppletion (Source: Oedekerk, 2006)

Fig. 3.9 Suppletion (Source: Oedekerk, 2006)

Fig. 3.10 An overflowing dike (Source: Oedekerk, 2006)

zone is under threat by suppletion. If enough space is created for natural processes and beach reserves are created, this negative effect of too much sand on the sandy coast that kills all life underneath, can be averted (Janssen, 2008).

Instead of heightening the dike, it is possible also to allow seawater to flow over de dike. This requires a strengthening of the inside slope with durable material (Fig. 3.10), which prevents the dike from being damaged. The overflowing water needs to be stored behind the dike or needs to be discharged. If the water is stored a second dike is required and in the area between the two dikes a wet zone, which is suitable for salt and brackish nature, recreation, saline agriculture and housing.

If an existing dike is opened and seawater is able to reach the hinterland, a new primary coastal defence will be necessary (Fig. 3.11). Between this new dike and the old one a dynamic area emerges, which floods regularly. This results in decreased wave pressure on the new dike. The area in between is rising because mud and sand sedimentates here. By enhancing these natural processes it is possible to keep up with the sea level rise. These higher altitudes in the landscape do have a positive effect on softening the waves and it increases the safety.

If seawater is allowed to enter the hinterland a regulated tidal inlet arises (Fig. 3.12). A transition area emerges where sea influence is apparent. This area is filled up with mud and sand at a place which meets the tempo of the sea level rise. Nature can be developed and this area is suitable for recreation a saline agriculture.

Fig. 3.11 Back draw of the dike (Source: Oedekerk, 2006)

Fig. 3.12 Regulated tidal inlet (Source: Oedekerk, 2006)

Fig. 3.11 Back draw of the dike (Source: Oedekerk, 2006)

Fig. 3.12 Regulated tidal inlet (Source: Oedekerk, 2006)

Land or seaward developments do have different consequences, especially on the long term. For the province of Zealand is researched for both directions how the province might be developed on the long term (Fig. 3.13). For both options a sound safety level is required. However, the option differ in the necessary space and the chances it offers for new functions.

If the defence is developed on land, especially in the agriculture the changes are felt, but it offers chances for nature development and temporary living areas (DHV, 2006). Seaward development offers chances for recreation, nature and energy. It leads to different images (Figs. 3.14 and 3.15).

Many of the solutions developed in the ComCoast project are adjusting the direct dike zone. Most of the solutions aim to create a multifunctional zone. The most limited solution seems the most realistic. Let the dike overtop with sea water, create an extra strong structure at the foot of the dike and let Many of the solutions developed in the ComCoast project are adjusting the direct dike zone. Most of the solutions aim to create a multifunctional zone. The most limited solution seems the most realistic. Let the dike overtop with seawater, create an extra strong structure at the foot of the dike and concentrate the seawater in a small zone behind the dike. Other solutions are creating broader zones with many functions towards the sea or inland, they are more expensive and require more space.

Fig. 3.14 Seaward development offers chances for energy production and leisure (Source: DHV, 2006)
Fig. 3.15 Landward development offers chances for nature and temporary living (Source: DHV, 2006)

The coastal defence can be limited to modifying the dike or the zone around the dike, but more far-reaching alternatives may be explored as well. The creation of new land in front of the coast is such a far-reaching idea, which is a very popular issue in the Netherlands. In the past and recent history many different ideas are explored. The background idea of all these ideas is that the realisation of a row of new islands is minimising the wave power, which minimises the chance at a dike breech. The easiest way to do so is the creation of a reef or long dike in the sea (Fig. 3.16), but it may be more inspirational if beside the defence also space is created for new functions.

Mother of all these visions is without doubt the Waterman plan (Fig. 3.17), in which a long island, suitable for urban functions, nature and recreation, in front of the South Holland coast is projected (Bos, 2001). The Bhalotra plan (Fig. 3.18) for

the same location is based on the same principles: at 500 m out of the coast in front of Hoek van Holland a long urban island should be realised.

Willem Bos developed plans and visions for the Western Dutch coast as well. He based his ideas on existing folds near the Maasvklakte and IJmuiden and created a hollow coastal curve (Fig. 3.19), where space is available for brackish wet nature in a strong and extended dune landscape, for bays with extensive beaches and for the existing harbours in between (Bos, 2001).

In the design that is developed by Adriaan Geuze for Boskalis a series of islands is created in front of the Dutch coast (Fig. 3.20). The islands function as protection for the coast, but create new valuable fishing zones in the North Sea also, because deep fishing spots are created by sand depletion at the right places. More new fishing area is developed than old ones are destroyed. Still, one can argue about the rationale behind this. Moreover, the islands enhance the development of new nature in the lagoon behind the islands and they support the sand transportation towards the Northern Netherlands.

A variant on the ideas of Geuze is the plan of the innovation platform (www.minez.nl). This plan proposes the development of a polder in the North Sea shaped in the form of a tulip (Fig. 3.21). The motion of member of Parliament Atsma, aiming to start a feasibility study on the realisation of such a polder was accepted by the House of the Commons by the end of 2007 (Atsma, 2007). The reasons to realise such a polder are not only the protection potential, but could also solve the spatial scarcity of the Randstad Holland, which can be solved in many other ways as well (other land reclamation area, intensive building options, shift to peripheral regions in the country). The shape of a tulip must be read as a symbol and not as a serious proposed form of an island.

A comparable way of thinking is followed in the research to realise a new airport in the North Sea (Flyland, 2003). The available space in the Haarlemmermeer polder

Fig. 3.19 Willem Bos' plan for an extensive hollow coastal bow (Source: Bos, 2001)

Fig. 3.20 Row of islands in front of the Western Netherlands coast (Source: Boskalis, 2008)

and around Amsterdam, without the hinder of noise contours, could be used for urban developments. This is only possible if Schiphol airport is moved towards sea.

The province of North Holland proposed a complete different island: an island for one season (Provincie Noord-Holland, 2007). This island should be realised without any coastal defence at 100 m out of the coast (Fig. 3.22). After a certain time this island will be erased and disappears in the sea, but during its existence it has a defensive as well as an ecological and recreational function. This solution seems to be very ineffective: relatively expensive and very temporal ecological function, if any.

Within the Grounds for Change project an island archipelago (Fig. 3.23) in front of the Northern Netherlands coast is designed (Roggema et al. 2006). These islands have several functions.

In the first place they contribute to the safety of the country by softening the waves during heavy storms and spring tide.

Beside this, the islands create a lagoon with quiet water, where sand sedimentates more easily. The increased sedimentation compensates the erosion because of an accelerated sea level rise. The increased amount of sand enforces the sandbanks to grow along with the level of the sea and doing so, the sandbanks keep falling dry during ebb tide. If the sedimentation is not increased it is expected that in 2040 about 40% of the sandbanks in the Wadden Sea might disappear (De Boo, 2005).

Thirdly, the islands offer the room for new functions, like housing, nature and recreation. Moreover, the islands offer the space for functions that, due to climate change, need to be removed from the mainland, like nature, which finds its northern boundary in the northern part of the Netherlands.

Part of the development vision for the Eemsdelta is the realisation of a new island North from Schiermonnikoog (MUST, 2007). This island (Fig. 3.24) hosts mainly economical functions, like a harbour where ships are able to enter with dirty cargo or ships that are too large to enter the Eems harbour or the Ems-river. Moreover, the island functions as an energy producer, using hydropower and windmills. In case of a storm, the basin gets filled up with seawater and the island softens the wave power on the coast.

In history and today many ideas for new (is)land in front of the Dutch coast have been proposed. Most ideas are developed for the Western coastline, because the weakest defence may be found here and behind the coastal defence the most valuable area is apparent. So far all ideas have not been realised. This is caused by the strange mechanism that the plans are judged in a technocratic way while the plans are visionary. Ideas to create a new world with many different functions,

Fig. 3.24 Economical energy-island in the Eemsdelta (Source: MUST, 2007)

where people live and nature is developing were judged in a way that the costs of the investment are compared with the costs of a safe defence only. A multi-functional development is seen as non-functional. The Netherlands is famous because of its engineers-solutions for defending against water, reclaiming land from the sea and control over the water management of canals, lakes and rivers. In such a country only the minimalistic and functional reasoning gives room for new solutions. There is no broader perspective available and there is no grand view or a senseless reason to create something rich. Because of its sobriety and thriftiness the Dutch never found the reason to create a broad and generous solution to defend the coast and realise an entire new landscape at the same time. With a rising sea level at stake, the ideas are presented again, but even in these circumstances the Dutch say: if the sand-grain can do the work, why should we build islands to defend ourselves. A new world of opportunities is out of sight, again.

3.2.6 Groningen Combinatory of Coastal Defences

A regular solution to protect the country from flooding is the heightening of the dike. This approach may solve problems if circumstances are not too extreme. However, if sea level rises more than a meter per century and storms become more intense, the dike needs to be supersized. This makes the system vulnerable. Even a strong dike can break and if a very high dike does, the damage is very large. Therefore, the vulnerability behind the dike is high and the resilience low as the people seemed and believed they are safe. If circumstances become extreme, and they will within the 21st century, another approach will be necessary. This alternative approach consists of the best combination of coastal defence measures. By implementing several measures at the same time, the vulnerability of the system decreases and resilience can be improved. For every specific area the most optimal mix of measures can be chosen.

The province of Groningen explored this multilayered way of thinking (Provin-cie Groningen and Climate Changes Spatial Planning, 2008). Several new coastal defence measures were judged and if proven useful they were mapped. If a certain measure could be used the locations will be shown on the map (Fig. 3.25). The different solutions are described here shortly. For a more extensive description: www.klimaatbestendiggroningen.nl: De kust van Groningen (Provincie Groningen and Climate Changes Spatial Planning, 2008).

COMCOAST COMPARTMENTS & SELFCARING UNITS DEL FZ IS LAND

ECODELTA SLEEPERD1KES SUPERD1KES

ECODELTA SLEEPERD1KES SUPERD1KES

SAND UNDERNEATH NEW ISLANDS HARBOURISLAND
Fig. 3.25 Nine new solutions for the Groningen coastal defence (Source: Province of Groningen & Climate Changes Spatial Planning,2008)

The nine different solutions for Groningen include the following:

1. Comcoast (see also Section 3.2.4) aims to create a coastal zone, where a multifunctional layout increases the possibilities to deal with high sea levels and storms. For example, one of the ideas is to let sea water flow over the dike.

2. Compartments and self-providing cells aim to create smaller compartments in order to minimise the effect of a flood to a small area. If, beside the compartments, self-providing cells are created, where people gather in case of a flood, the damage can be kept to a minimum.

3. Delfzisland (see also Section 7.3) creates a floodable zone around urban concentrations. Seawater as well as a surplus of rainwater can be stored in this area temporary.

4. Ecodelta creates a broad coastal zone, where ecological development is combined with an attractive new living environment.

5. Sleeper dikes are old sea dikes, which ran out of function when new land was reclaimed and a new sea dike was build. If the old dikes are restored and maintained they may very well function as a secondary defence. If the first dike breaks, the sleeper dikes prevent the water from flooding the entire hinterland.

6. Super dikes are extra broad dikes. If dikes are broadened it is hardly possible to break them. It may be possible that water flows on or over the dike, but a breakthrough is hardly possible.

7. Sand Underneath proposes the extra heightening of urban concentrations with sand up to a level that will not be reached by a rising sea level. This way the urban areas can be kept safe.

8. New Islands are protecting the coast because they break the heavy waves in case of high tide and a storm situation. If the islands are positioned right they are not only minimising wave power, but are capable of creating a quiet lagoon-like wetland behind them.

9. Harbour-island also aims to protect the coast by breaking waves, but combines a function as harbour with the production of energy. Windmills and a fall-lake in combination with tidal, wave or osmosis plants are giving the island an energy image.

If all measures are combined on a coastal mixture map (Fig. 3.26) it becomes clear which measures are best to combine in specific areas. This combination of coastal defence measures optimises the protection at every location along the coast, but it enhances a multifunctional development as well. Finally, the combination of measures offers higher resilience, which makes the society less vulnerable for floods.

The approach to combine several good solutions at suitable places along the coast is attractive, because it offers extra safety (if one defence option malfunctions, the next one still does), it is possible to create at every small place a solution which is made to measure, it offers the chance to combine new functions and it offers the change to experiment with innovative solutions, which would never have been used if they were the one and only defence mean at a certain spot.

Fig. 3.26 Combinatory of Groningen coastal solutions (Source: Province of Groningen & Climate changes spatial planning, 2008)

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