Graduation work by Hannah de Winter.
Extreme precipitation causes nuisance in daily life in many urban areas. This thesis researches possibilities to create an adapted sustainable environment by using a landscape based design approach with Veenendaal-oost as pilot case. This approach searches for a renewed connection with the landscape and seeks for site-specific challenges and opportunities the landscape offers.
In many urban areas, problems related to the water system occur during and after extreme precipitation events. Those problems ask for fundamental changes and sustainable solutions. In the most ideal situation a return to the natural water level is desired, see illustration 1. It would be best to incorporate measures that offer multiple benefits, in example for recreational purposes and living comfort [Short et al., 2012, Wamsler et al., 2013].
Illustration 1. Left the water cycle in urban areas, where a lot of water flows away due to the amount of surface which does not allow water to infiltrate. In nature areas, on the right, infiltration does occur which limits the amount of water flowing away via the surface and limits nuisance and flooding.
For new urban areas, such as the pilot case of Veenendaal-oost, it would be best to build for resilience and live with the risk of flooding. This is also called flood resilience, in which the (urban) landscape maintains its most important processes and characteristics when subjected to a flooding. To create an adapted environment is a complex process that requires cooperation between different disciplines [Short et al. 2012].
It is not only adaptation of existing urban environments that is needed. Due to climate change more and more extreme precipitation events will occur in future. This might need adaptation of whole environments in future. The KNMI developed four climate scenarios for the Netherlands in which precipitation is taken into account. The worst case scenario related to precipitation is the W-scenario that will be taken into account in this study [Klein Tank and Lenderink, 2009].
Since the increase of extreme precipitation events is a structural problem and whole environments are influenced by it, it is interesting to search the possibilities of the use of the landscape based design approach. This approach addresses issues such as cultural identity, fragmentation of landscapes and diversity. It has an ecological and geographical sense and contributes to the development of site-specific solutions. It also strengthens the landscape qualities and make it possible to create a sustainable landscape [Koh, 2009].
By using the landscape based design approach it is possible to create a design that does not only prevent the urban environment from flooding, but which strengthens the landscape as well. The analysis of the landscape is very important in this approach and requires some special attention. The location of the pilot study is in the Binnenveld area, the southern part of the Gelderse Vallei. Illustration 2 shows an intersection of this area and shows the location of the site. Due to the unique setting of the area, seepage occurs which creates circumstances that bring high ecological values to the site [Brons+Partners, 2005].
Illustration 2. The Gelderse vallei is created in the Pleistocene period due to ice caps. The first settlements took place on higher grounds about 10.000 years ago. Since 150 years there is reclamation and urbanisation on larger scale. The pilot area is situated at the location of the pink arrow.
For the pilot area this means that ecological ambitions play a role. Here is a focus on the Kamsalamander, a specie that needs ponds for breeding, living and safety. Those ponds must be disconnected from the general water system. The specie is not disturbed by humans and the habitats need to be within a range of 500 metres [De Putter and Boerefijn, 2010].
Besides the ecological ambitions there are also ambitions set for urban developments, recreational opportunities and of course the water challenge for the area. For all of those aspects, suitability studies have been performed in which the requirements of the land-use type are taken into account. In example the requirement of at least one metre dry soil for a suitable location to build on. Those requirements are combined with the characteristics of the site like average water level, soil type and height. Result of this are various suitability maps that show the most ideal locations for the different types of land-use based on the strengths of the landscape. Result of the study for the pilot area is that water buffer can be best situated in the low areas at the west, urban development should take place on the higher grounds in the east and an ecological zone will be situated in the middle of the area.
Another important part of the landscape based design approach is the perception study of the pilot area. This is performed with as main goal to seek for the site specific characteristics of the area. This perception study is performed by walking, cycling and driving through and around the area, at different moments in the year and different times a day. By doing this it was possible to experience all kind of aspects related to our senses. Thinking of a smelly farm, a noisy road, views towards the hill ridges. Combined with knowledge about the history of the site, gained by meetings with experts and analysis of historical images and maps, it is possible to really get to know the landscape in depth. As a result of this study is stated that it is important to remain / strengthen the views over and through the landscape. To restore and strengthen the east-west structure of the site which is a remain of the peat distraction period. Buildings should be placed on higher grounds and the wet landscape should be created in the lower areas of the site.
Since the qualities and strengths of the landscape are very important in this design process, it became a challenge to create a concept of the site. The municipality has set an ambition of 3200 new dwellings for the site, but this might conflict with the character of the area. To seek for possibilities and solutions, 24 quick concepts were created which all addresses some strengths but which sometimes also show weaknesses. Main questions that arise are: is it possible to build 3200 dwellings while remaining the character of the site? How is it possible to combine openness with the east-west structure? And is there enough space for the ecological zone?
Since the amount of dwellings seems to limit the possibilities in the site, an assessment on this is performed. This shows that there will be more elderly people in the village in future, who might need other facilities. Besides that, the current developments in the village do not sell as expected. But locations that do sell are most of the times special plots, larger plots surrounded by an unique environment. So it would be interesting to focus on high end living for which the landscape will eventually show the carrying capacity when it comes to an amount in dwellings [Ritsema van Eck, et al., 2013].
The waterproof aspect of the environment will be leading in the design. That part should be functioning well and creates the base of the design. Illustration 3 shows the design with focus on the water system for the pilot area. You can see that in the west there is a water buffer area situated, where water is stored during and after extreme precipitation events. The form of the water structures is in line with the east-west orientation of the landscape and thus strengthens one of the landscape qualities. With larger water canals, water from the east is discharged towards the buffer area.
Illustration 3. The design with focus on the water system to prevent flooding causing nuisance in the urban landscape. New water canals discharge water from the east towards the buffer area in the west.
In the end there will be space for almost 2000 new urban dwellings along the new east-west oriented water lines and on higher grounds. There are three larger building blocks that connect the area with the existing village. It also contributes to the awareness of living in a water rich environment and shows the impact during and after extreme precipitation on the environment. Illustration 4 shows the changing environment around one of the building blocks during and after extreme precipitation.
Illustration 4. The southern building block in the water buffer area. In different phases the site floods which changes the environment and creates awareness of the impact of precipitation on the landscape.
A new ecological area is created that is well suited for the Kamsalamander and also for other species in the area. There is a maximum distance of 500 metres between the ponds and they are disconnected from the general water system as required. Along the main roads, the green structure is strengthened which is done in line with the existing character of the site. This green structure contributes to the appearance of a green horizon which makes you feel like the city is far away. There is also an extinction of the recreational paths, not only along roads but also through the area itself. There is a proper connection with the existing village and the surrounding environment. Nature and recreation are well combined. There is also a distinction in paths for different types of users which contributes to the comfort of people visiting the area.
An important character of the site was the views over the landscape that make you experience an open environment connected to its surroundings. Those views were strengthened where possible and with that this character is maintained in the area.
With the landscape based design approach it became possible to create a landscape in which multiple benefits are integrated. The character and strengths of the landscape are maintained while the quality of the site is improved. Illustration 5 shows one of the new urban areas along a new water canal. The elements present here show that it is possible to combine the landscape characteristics with urban development and recreational use of the site.
Illustration 5. Impression of a neighbourhood along a new water canal. Different functions are combined: water discharge, urban development and recreational purposes.
In the end can be stated that the effects of climate change are undeniable. We need to adapt our environment towards this. In the current situation, adaptation is mainly focussed on management or site specific level. With use of the landscape based design approach an adaptation strategy for new urban areas is found, which also takes the environments strengths and qualities into account.
Brons+partners. 2005. Landschapsontwikkelingsplan Gelderse Vallei. Gemeenten Amerongen, Barneveld, Leersum, Leusden, Maarn, Renswoude, Scherpenzeel, Woudenberg.
De Putter J., and M. Boerefijn. 2010. Contouren voor het Waterinrichtingsplan Groene Grens. TAUW. In opdracht van: Gemeente Veenendaal.
Klein Tank, A.M.G. en G. Lenderink (red.). 2009. Klimaatverandering in Nederland; Aanvullingen op de KNMI’06 scenario’s. KNMI. De Bilt.
Koh, J. 2009. Landscape is What – Landscape is How. On a landscape approach to contemporary urbanism.
Ritsema van Eck, J., Van Dam, F., De Groot, C., and De Jong, A. 2013. Demografische ontwikkelingen 2010-2040. Ruimtelijke effecten en regionale diversiteit. Den Haag: Planbureau voor de Leefomgeving.
Short, M., W.L. Peirson, G.M. Peters, and R.J. Cox. 2012. Managing adaptation of urban water systems in a changing climate. Water resource management. Vol. 26. P. 1953-1981.
Wamsler, C., E. Brink, and C. Rivera. 2013. Planning for climate change in urban areas: from theory to practice. Journal of Cleaner Production.
november 24, 2014