At work (at a local authority), I have a flood zone plan/layer that was created using ArcGIS software from an Elevation Model which has an accuracy of 1 metre. The zone covers an urban area. I cannot get to the resolution of which buildings will be more effected by flood and which won't, but I do have a layer of all buildings.

The question is, whether I should cut the buildings out of the flood zone, and why?

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    $\begingroup$ what is your ultimate aim? Are you trying to create a layer which only has building that will be flood affected? $\endgroup$
    – Fred
    Commented Jan 22, 2016 at 12:52
  • $\begingroup$ Hi Fred, thanks for the reply. I need to create the flood zone at the moment. Later I will use it for risk of population, risk to property and emergency services $\endgroup$
    – Mick
    Commented Jan 22, 2016 at 12:54
  • $\begingroup$ @Mick interesting question. I am wondering why you would consider cutting the buildings from the flood zone; especially if you will later model the risks anyway. Could you share with us why it is an issue for you to either cut (or not) the buildings - it will help us to answer/discuss better $\endgroup$
    – marsisalie
    Commented Jan 22, 2016 at 14:09
  • $\begingroup$ @fre0n because maybe buildings in general tend to be protected from floods (that's merely an assumption with no base) especially commercial buildings. I guess that the question is whether the majority of buildings would be sealed to water when there is a flood outside $\endgroup$
    – Mick
    Commented Jan 22, 2016 at 15:02
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    $\begingroup$ Some buildings are designed for flooding; many are not. There is probably not a universal answer to such a question. But... I imagine that what you should do depends on the purpose of your GIS layer. $\endgroup$ Commented Jan 22, 2016 at 17:36

1 Answer 1


Since it is not known at this stage what measures were implemented for each building in regard with eventual flood situations, it does not make sense to purposely exclude the buildings from the flood zone until some kind of general database with that info is built and put into context in your system. Even-more, a lot could happen in a potential flood zone when an extreme event occurs, regardless of the prevention plan by various owners and city management. A risk management model with proper risk probabilities, potential damages and monetary values would eventually be required to better represent the up-to-date context of the site.


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