Tag Archives: Climate adaptation

Climate proof Leiden: simplicity is key

Overwhelmed by new initiatives for tackling the effects of climate change nearly weekly, I got lost within this stream of ideas a long time ago. Each time I get confronted with technically complex product designs, my initial thought about creating new techniques and designs pops up. Why do we constantly have to come up with advanced and innovative ideas, when we can achieve so much with already existing ideas and products?

Take for instance Leiden. This Dutch city, also known as Sleutelstad (Key City), is a densely built-up city and municipality in the Netherlands. The inhabitants of Leiden are quite familiar with the abundance of water in the streets after high amounts of rainfall, which is getting worse year by year because of climate change. Especially the northern districts of the city have difficulty coping with high amounts of rainwater regularly, mainly because of the low-lying area the districts are located in and the further subsidence of the houses over the years. Adaptation is therefore highly essential to adjust to the short-term effects of climate change.

Flooding in Leiden due to heavy rainfall. Source: leidennoord.nl

A wonderful and simple invention that can easily contribute to tackling this problem is the rain barrel, a product we already use for centuries to collect rainwater. As stated by WWF, not only is the usage of rain barrels a great way to conserve scarce freshwater, it is also a simple and cheap step to reduce flooding as a result of heavy rainfall. Different sizes and materials are available when purchasing a rain barrel, but the overall rule is that it should not take any effort to connect the barrel to the downspout. Taking into account that watering your garden can account for a high percentage of domestic water consumption and that you can easily use rainwater for flushing your toilet, installing a rain barrel could possibly save you quite some money and prevent you from using much more water than necessary.

Example of a rain barrel connected to the downspout. Source: extension.usu.edu

The municipality of Leiden has tried to encourage the usage of rain barrels in 2009 by offering free rain barrels to the inhabitants of district Groenoord-Zuid. Despite the fact that 60 households were interested in participating in this project, the municipality has not actively continued encouraging the usage. Therefore it is time for action.

Major repairs and renovations within the city will not be enough to fully adapt Leiden to the rainy effects of climate change. Collaboration and participation of the inhabitants is also required to prevent everyone from having wet feet. In fact, to prevent flood damage, more and more municipalities obligate their inhabitants to collect rainwater from their downspouts with rain barrels. An active attempt like this would suit Leiden, especially because of their past experience with the abundance of water in the streets.

The solution for the water problem in Leiden does not necessarily have to be completely technically complex. Maybe by looking for straightforward measures as the key for adaptation, a climate proof Leiden is achievable sooner than we might think.

How to: from grey to green and blue


The first time I was personally confronted with the effects of climate change was when I woke up from a weird banging sound above my head. My neighbour was walking on my roof, sweeping water over the edge, because he was experiencing a leakage (by doing this he caused a leakage in our roof, but that is another story). The intensity of rain showers increases due to climate change. Add this increase to the surface cover in cities, and you have a big problem. Most cities are ‘’concrete jungles’’: the largest part of the surface consists of concrete or buildings made of stone. Rain cannot infiltrate into the ground due to all this stone, and the showers are too intense to processed by the sewage system, which can result in flooding (or a leakage in my case).

Big cities all over the world have to adapt to the (future) climate. This climate will pose some challenges on cities like Amsterdam, Rotterdam and Leiden: the intensity of rain showers will increase, droughts will occur and higher temperatures will occur more often and for prolonged periods. Heat becomes an enlarged problem in city centres. To make it even more complicated, the city itself is enhancing these high temperatures. Due to the large amount of concrete and stone cities are made of, they expose the Urban Heat Island Effect: the temperature in the city is often higher than the temperature of the surrounding area. For example, in Rotterdam, the difference in temperature can rise to 8 °C.  (source: http://www.rotterdamclimateinitiative.nl/nl/dossiers/klimaatadaptatie/themas/warmte-in-de-stad)

Urban Heat Island Profile. Source image: http://geography.name/urban-heat-island/


Green and blue

Luckily, part of the solution to cope with the effects of climate change is already present and ready to be used: green and blue. Why these colours? If more water (blue) and vegetation (green) are present in a city, rain showers can be retained and infiltrate more easily, so the amount of rainwater that has to be processed by the sewage system is reduced, which decrease the risk of flooding. In addition, green and blue both cool their surroundings. This cooling effect is much needed and wanted in periods of heat in the city.

However, another part of the problem is that cities are densely populated, so little or no space is available for more water or vegetation. So, we need more blue and green but there is little space available. How do we still implement it?

Smart use of space and combining of functions is necessary when we are talking about big, densely populated cities. One of the great examples of combining social and water retaining functions is present in Rotterdam: ‘water plaza Benthemplein’. To see a video about the water plaza, press the following link:https://www.youtube.com/watch?v=kujf4BTL3pE For more information about the water plaza in Rotterdam, visit: http://www.urbanisten.nl/wp/?portfolio=waterplein-benthemplein

Water plaza Benthemplein in Rotterdam. Source image: http://www.theneweconomy.com/technology/rotterdams-water-management-gives-rise-to-exceptional-city

Public squares in Leiden can also be converted into these kind of water plazas. These squares will not only contribute to a climate adapted Leiden, but will also improve the ‘face’ of the city and social connections between its citizens.

One of the easiest solutions to prevent flooding and heat is replacing grey by green: stimulating citizens to replace stone in their gardens by plants. Leiden already is participating in ‘Operatie Steenbreek’ http://www.operatiesteenbreek.nl/, which is an organization with exactly this goal. Another smart solution is using already existing buildings, especially their roofs. Roofs can be converted to so-called ‘blue roofs’, which can be used for rainwater retention. An additional benefit of water roof is its cooling effect in the summer.

Intensive green roof. Source image: http://www.groenblauwenetwerken.com/measures/green-roofs/intensive-green-roofs/

The other option is a green roof: a roof covered with vegetation. Roofs can be covered with various kind of vegetation: flowers, moss or even trees. Apart from the retaining of rainwater, green roofs offer more benefits: they can increase biodiversity, cool the surrounding area and cool the house itself. For Leiden, green roofs have an additional benefit: seagulls don’t like green roofs to breed or rest on!

For Leiden, many options are available to become a climate-proof city. It will be challenge because of its densely populated, stone covered city centre. However, a lot of possible solutions are available. Green roofs and watersquares are just a few of them. If you are interested in implementing blue and green in cities, visit:http://www.urbangreenbluegrids.com/

If me and my neighbor both convert our roof to a water roof or a green roof, we will hopefully prevent other leakages, reduce the risk of flooding of our street, cool our surrounding areas and can enjoy a cool house during hot summer days. We can make our cities climate-proof and livable. Let’s turn grey into blue and green!





Live with water, don’t fight it

In 1953, the dykes broke. One of the biggest disasters the Netherlands has ever suffered. Since then, we managed to set up one of the most extensive flood protection projects in the world. Our feet have been dry ever since.  But, the tide may be changing. The Netherlands will get hotter, drier and wetter. According the Climate scenarios from the KNMI we will see more and more extreme rainfall towards 2085. Next to that, in between these extreme events, there will be dry periods. Whether you like this or not, it raises the question: ‘’Are our cities ready for the future?’’

Flooding in ‘de Kooi’, Leiden

It is not just a future scenario. It is happening already. Extreme showers will happen more frequently and will be heavier. This leads to certain problems. For example, in cities like Leiden, the sewage system isn’t able to cope with the extreme amounts of rain that will fall during short periods of time. This will result in flooding in streets and houses, which leads to lots of damages. Already this has happened in Leiden.

Cities are most vulnerable because of increasing urbanization. This causes problems with increased flash flooding after sudden rain. As areas of vegetation are replaced by concrete, asphalt, or roofed structures, the area loses its ability to absorb rainwater. This rain is instead directed into the city sewage system, often overloading it and causing floods.

Example of a wide ditch

Municipalities can take measures to prevent the streets from turning into rivers. Some more natural examples include, more green and wide ditches/ponds  in suburbs to allow the ground to take up more water. On the other hand, a more mechanical solution is building surface water drainage systems to relief the sewage systems by transporting rain water to rivers or basins.

The solutions named above may not always be possible. For example, there might not be enough space for creating green areas, which is the case in Noorderkwartier, a district in Leiden. I think especially in those areas it is vital to let the citizens know what problems the council is facing in protecting them. With the right incentives, communities can transform their own neighbourhoods in flood save and sustainable places to live. Below are some solutions people can take to achieve this:

  • Green open gardens. Paved gardens direct water straigt into the sewage system. Green gardens on the other hand, absorb water and also look more attractive.
  • Installing water butts. Green gardens need water. Instead of tapping fresh water, a more sustainable way is to collect rain water. If all houses in a neighbourhood have one, it might just be enough to take up the first beating of a heavy shower. A more advanced idea is the collection of rainwater in large tanks and use that water in a so called ‘grey water system’ (see picture below).


  • Green roofs. This is a more challenging solution. Roofs are large surfaces, which potentially can take up a lot of water if planted with grass. However, roofs must be able to support the weight of them.

Let’s embrace these solutions and turn our paved surroundings into green sustainable neighbourhoods where rain is welcome.

After us a garden


Après nous le déluge’ was alledgedly said by Madame de Pompadour a French aristocrat from the 18th century and mistress to King Louis XV of France. ‘Après nous la deluge’ or ‘after us, the deluge’ roughly means ‘I do not care what happens after we are gone’. However, I am glad to say that a lot has changed since that statement was made, but a different threat looms over us.

By now the majority of the population is aware of climate change and cares about the state in which we leave the world to future generations. Furthermore, we ensured that chances of heavy flooding are as slim as the chance of experiencing a guillotine induced death. But there is a different water-based threat to suburban life and it arrives in the form of heavy rain fall. Spells of rain will become short and severe, instead of long-lasting and drizzly, this is caused by climate change. Therefore, we need to make sure that our inner-city drainage can handle a lot of water in a short period of time.

I personally live on the outskirts of Leiden in a neighbourhood with a lot of space for plants and trees to grow. After the rain, I can see puddles but after a night or a part of the day I notice that all the water is gone. When travelling to the city centre the predominantly green environment changes into brownish manmade surroundings with more Apple-stores than apple trees, and more Lush-soap shops than lush vegetation. After a spell of rain, you can still see puddles for a long time. Heavy rainfall already causes problems in certain parts of the city, where rainwater can reach over the thresholds of waters and flood into people’s homes. It seems to me quite an inconvenience when a whole neighbourhood collectively shudders and frantically reaches for the hosing-bucket at the sight of a low hanging dark cloud!

Clearly a solution is needed for the watery threat from above, rather sooner than later I would like to add. I personally think that where possible green spaces must be created. So-called raingardens or Sustainable Urban Drainage System (SUDS) can be offer a pretty solution to an ugly problem. Raingardens aide in the capture of water in a natural manner, and making plants and flowers grow and bloom creating small bits of green or parks. Plants and flower store water in their roots, but their roots also bind the soil protecting against soil subsistence. Raingardens make the underground struggle against excess water visible and part of our day-to-day lives. The presence of nature in the form of flowers and plants also have an effect on the psychological wellbeing of people. A certain quote from Ladybird Johnson comes to mind when writing about raingardens ‘Where flowers bloom, so does hope’. For the inhabitants of regularly flooded neighbourhoods this might be the hope of permanently keeping their feet dry. Let us leave a garden for future generations to enjoy!

Awareness is created by explaining what  raingardens do, but the benefits are mostly noticeable by the absence of flooding after heavy rainfall. If you are interested in raingardens or other forms of Sustainable urban drainage systems I would recommend reading the following articles.



Sustainable Leiden – Jan 2017

A new year, new chances! The students of this year’s final course of the Minor Sustainable Development, provided by the Institute of Environmental Sciences (CML) at Leiden University, will again be working with the Leiden City Council to help them develop their Sustainability plans. This collaboration was started last year, and we look forward to building upon its success.

Image result for innovative ideas from waste
Plastic bottles to create a vertical garden (pic credit: Maria Rose)

As part of this course, students will be investigating the opportunities for the city of Leiden with respect to energy generation, energy transition, circular economy and climate adaptation. In groups, they will address specific questions of the council regarding these topics, and present them at the end of January. In preparation for this exercise, the students will be writing posts to this blog detailing ideas and initiatives from elsewhere as inspiration for what may be done in Leiden.

We look forward to presenting some exciting ideas appear over the next few weeks!




Green roofs to make Leiden future-proof!

If we look at climate adaptation of the city of Leiden, the main goal is not to fight nature, but to work together with it. While climate is changing, life in the city changes as well. The more extreme weather causes floods, droughts, higher and lower temperatures and the city cannot always handle this. That is why it is necessary for the city of Leiden to adapt to the climate. One way to do this are green roofs. If you do not know what a green roof is, watch this video to know all the basics.

Green roofs can solve a lot of problems that climate change brings. Green roofs absorb water during heavy rainfall, so that sewers do not overflow. Green roofs keep the inhabitants cool during the hot summer and most of all, it keeps people dry. Also green roofs can provide a habitat for wildlife to increase biodiversity and it can increase the air quality in cities (Oberndorfer et al. 2007). Green roofs mean less consumption of energy because it keeps you warmer in the winter and cooler in the summers.

Green roofs will become also more economically attractive in the future. Now a green roof is in comparison with a traditional roof 10-14% more expensive at a life span of sixty years. If the climate keeps changing and extreme weather will occur, the green roofs will become more and more attractive to prevent flooding and extreme heat in cities because of saving money on energy consumption and other techniques to prevent flooding (Castleton et al. 2010). There is an initiative in Leiden to get more green roofs. It is called Groene Daken Leiden and helps citizens to get subsidies for green roofs. It is based on an initiative of Amsterdam and it is making great progress. If you want more green roofs in your neighborhood you can ask them for help to get subsidy. Then you can help Leiden to adapt to the future in a more sustainable way for only a small fee. In the picture below you can see a project they did at the Boerhaavelaan in Leiden.


The benefits of green roofs are endless for the environment and for the people living under them. Green roofs are a great way to get more green and plants in the city and increases the aesthetic value of neighborhoods. Green roofs are also a great method to reduce noises and living in a busy city this can be of great value! Green roofs does not demand a lot of maintenance. Only in periods of drought is it necessary to water your roof, but even a dryer roof will keep all it functionality and benefits (Getter & Rowe 2006).

Leiden is a very dense build city and has a strong heat island effect. This means the temperature in the city is on average 3 degrees Celsius higher than in rural areas. With rising temperatures because of climate change this can cause a lot of problems for the city, such as droughts and higher mortality rates during heat waves. If we want to keep the city a nice place to live, things have to change for future generations. Green roofs can provide a solution to make Leiden future-proof!

The Netherlands as the next Atlantis; are you prepared?

The Netherlands is known for its intensive way of managing the water. Without this intensive management with dikes and of course, the ‘deltaworks’, The Netherlands wouldn’t even exist for a big part. 26% of The Netherlands is beneath the sea level and almost 60% of the land is vulnerable or sensitive for floods. But what does this mean for you and me? Does the average Dutch citizen dwell on the fact that they are this vulnerable? And do we know what to do in case of an emergency?

Figure: landkaart Nederland met opverstromingsgevoelig gebied (PBL); 59% van het landoppervlak van Nederland (dus excl. Waddenzee, IJsselmeer en ander open water) is gevoelig/kwetsbaar voor overstromingen
Flooding sensitive area in The Netherlands

To raise the awareness about the existing flooding risks, the government came up with a special website and even launched an application for your smartphone on the testing day of the Maeslantkering in 2014; www.overstroomik.nl. At this website and application you can find out if you live in a risky area, and how high the water will be if there will be a big flood. For Leiden the chances are pretty small that we will be completely flooded. The centre of the city is surrounded by dikes, but there is still a risk that you get flooded. For example, the station would be flooded with 2 metres of water. But what is the actual chance of a flood? The chances are smaller than 1%, but it could always happen at an unexpected moment, like tomorrow.

The website even gives advice whether you should stay or go. The most likely thing to do is to stay, except of course if you’re city is 4 meters under water. One important reason for this, is that most of the highways in The Netherlands are quite low-lying. But if you’ll stay, you have to be well prepared. There will be no more electricity, no sewer system, no more running water from the tap. This means that everyone in The Netherlands should have some warm blankets, water and food, a radio on batteries, flashlights, candles and a lighter in stock.

If you decide to leave your house and find a safer play to stay, there are several things that you have to keep in mind. First of all, you need to take some basic things like food, water, medication, blankets and of course warm and dry clothes. Take care that you have enough fuel to reach a safe place and make sure you keep your family updated, so they don’t have to worry.

Website overstroomik.nl

But to be honest, who thinks about the real possibility that The Netherlands will be flooded? Are you prepared if it happens tomorrow? One thing is sure, there are several people and companies that take advantage of the fact that we live a land that lies below the sea level. If your house is in a risky area, you can protect it by applying several protection doors and gates, which you can find among other places here.