Thor and the seven monsoons
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Thor and the seven monsoons

By maxnl on

 

Code yellow!

We have seen it many times this summer. And we may see it again before the end of it. Code yellow… Code orange even, once or twice. The provinces get beaten up by hail, electrocuted by lightning, and flushed away by crazy amounts of rain. Rain, that I only remember from distant vacations… Torrential rains that pour down like monsoons! And I don’t know if you have the same experience, but I don’t really remember this from my childhood… Sure, it always rained like crazy, we Dutchmen complain about our summers for a reason. But not like this… This is special…. And if that is climate change… Well, I cannot say anything about that, I’m not a climatologist. Let’s just say in a good old Germanic fashion that Thor aka Donar, the God of the weather, is in a huge battle with the other Gods. They are really on to it!

What you probably also noticed, just like me, is that our landscapes can only handle this weather to a certain degree. Especially the extreme rain is a big problem. I live in the centre of Utrecht, and so in an urban landscape, and I have seen my street turn into a white-water river twice this summer. One would expect that from Bangladesh or something, right?!?! But apparently that has also become our reality…

It’s here to stay…

We will see this more often. Our sewer systems were clearly not designed for this, and ‘quickly doubling them’ doesn’t sound like a feasible option. We will have to deal with all this water WITHIN the landscape. We will have to keep it there longer, and to gradually release it to the sewer system. And it looks like we will have to set concrete steps in this direction very rapidly, because the problem is already here, and the solutions inevitably come later…

Water in the landscape… Keeping it longer, before it goes ‘down the drain’. Less closed surfaces like asphalt and concrete are a partial solution. Green roofs! Adding more open water to the landscape, or also ‘wadis’, laying dry when water is not there, but capturing loads of water when the time is there. Not that there is any space in my small urban street for a canal or a wadi…

And now about us!

What strikes me as a geo-person, is that this actually is a fairly straightforward spatial problem. This is a spatial problem, and I seem to recall that ‘we’ as geo-people were quite capable of handling these type of problems. We can capture, monitor, calculate, analyse and solve these problems. That was our cup of tea, right?!? Correct me if you feel the need to, but I have the feeling the geo realm is not involved into this problem enough by the climatologists, hydrologists, meteorologists and whichever other relevant –ologists. And vice versa: I don’t feel that we understand that we can add something to that discussion! We really have a relevant opinion on these matters, and we can really add some relevant expertise to the table! We really should get on our feet and start working on this theme!

So what can we do then? Well: We can model this water problem very well to start off with. You thought that that has already been done? Well…. That is kind of disappointing I must say. But there are water models, in environments like SOBEK and 3Di and the like, right? Mmmwwyeeah… That’s correct, but they are fairly course-grained.  And there should be models like that, that not a bad thing. But if you want to model the flow of water through my street, you would have to model the kerbstones. The speed bumps. The curvature of the road. If you don’t have details like that, you know too little. And to break through a myth: the Dutch LiDAR flown AHN (Actueel Hoogtebestand Nederland: Dutch current height model) height dataset is not accurate enough to consistently model this. It lacks two things: the spatial resolution is too low. The sampling distance needs to be smaller to model things like this. And it also lacks another resolution, being a temporal one. A new file every ten years is simply not enough. We need an annual update. If a furrow in a field has an enormous effect on the water flow direction and the ability to hold water for longer periods of time, then you will have to be able to model this furrow. AHN will not be able to offer this ability.

And now for something practical…

We could extract height models from stereo aerial photographs on an annual basis, with high spatial (5cm, 2 inches) and temporal (annual…) resolution. That will give you the curvature of the road, and if the road gets resurfaced you will have that information as well by next year. This also gives us a lot of information about the inclination of rooftops. Did you know that a green roof  -with seriously positive effects on the gradual release of water to the sewer system- works best on a roof with a 5% inclination? For truly flat roofs you need a drainage system, and with larger inclination angles you need to construct terraces. But we can calculate that stuff, we geo-people are good at that, right?

Another big question is if a surface is closed or open. And if it is closed, if it is half-closed or totally closed. These are parameters that we can give concrete answers to using remote sensing. We can define if the soil is covered with bricks or with grass, right? Even in back yards, where not a single government registration has any information on? We have all the means in place to model a percentage of closed surface.

And next to that we have datasets with open water, with water tables, with soil types, with the works! And weren’t we the masters of combining datasets to turn make sense out of apples and oranges? To use location as the foreign key between otherwise incomparable datasets? That was what we do for a living, wasn’t it? We can define what the effect is of a half open surface on top of a certain type of soil with a certain ground water table underneath. That’s just a few good GIS queries away!

Geo to the rescue!

It’s about time that we as ‘geo-ilites’ start joining the round table discussions on this topic. Others may understand water better, I will definitely admit that. But we are nonetheless a full-blown discussion member on this topic. We can come up with very concrete partial answers for this discussion. And we better start joining these discussions right now! Because Thor isn’t finished with using monsoons as a weapon any time soon, that’s likely going to get worse in the years to come …