[Qgis-user] Calculating affected regions of high-water situations

[Andreas Neumann]

Hi Werner,

Thank you for your info. I came across your Wiki page and also across
TAUDEM (doesn't seem to offer what I need) - at least not as an ready-to
use tool. I also came across r.hazard.flood - I will investigate this
tool further.

I was hoping to do a simple GIS analysis for detecting flooded areas
along bigger rivers in Switzerland - as a student work for a course.
Therefore the model doesn't have to be very sophisticated. If it turns
out as too complicated with OS tools, I may have to skip the idea and
look for other scenarios that are easier to solve with OS GIS.

I thought that this is a common use case in GIS - as many communities
have to do the "Gefahrenkarten" - risk maps. But probably this work has
been outsourced in most cases to real hydrology experts. Then these
hydrology experts probably do not want to make the process too easy and
available to the average GIS users - otherwise they would loose their
jobs/contracts ;-(

Thanks anyway,
Andreas

Am 11.12.2012 00:20, schrieb Werner Macho:
> On 12/10/2012 01:01 PM, Andreas Neumann wrote:
>> Hi all,
>>
>> I am looking for tools for calculating the affected regions when a river
>> level rises 1, 2 or 3m. I have DTM data (2m resolution) and cadastral
>> data with the areas of the flowing water bodies at hand.
>>
>> Are there any tools that can help me get the affected raster cells in
>> the DTM if the river level rises? With a lake, it would be a bit easier,
>> but the river also has a slope ...
>>
>> I am ok with any OS GIS solutions (GRASS, QGIS, Taudem or Saga, etc.).
> Hi Andreas,
> 
> That's the area I worked in for the last 7 years. To be honest (and you
> already mentioned it) it's easier in GIS with a larger area (lake).
> I expect you already know tools like r.terraflow in GRASS GIS (Probably
> not - that would be the first point to look at)
> Due to the nature of rivers it is not so easy to rise river levels
> (depending on the width of the river).
> There are also r.inund.fluv and r.hazard.flood so it seems with just GIS
> you have to use GRASS here - though I don't know about the reliability
> of this tools.
> 
> As I studied hydrology and hydraulics there are a lot of proprietary
> tools out there that can calculate what you need (and a lot more) like
> TUFLOW and Hydro_AS-2D (with Hydro_AS I used to work for the last 7
> years). But I think that would be a bit too sophisticated for your
> needs. In my work I needed tools that can do such predictions with an
> accuracy on a cm base so probably all my coming answers are too much
> work for your needs.
> 
> With Opensource it can maybe be done with Taudem or ANUGA but I did not
> have the time until now to take a closer look at this opensource tools.
> That would be the point where Pete Wells from Lutraconsulting could jump
> in :).
> The only tool I have experience with is (free) BASEMENT which is being
> developed at the ETH Zurich but preparing the model and calculating it
> with BASEMENT is nearly as complex as doing it with Hydro_AS (due to the
> fact that both programs are using the same type of input models). But I
> know that a group at the ETH is already working on a QGIS Plugin to make
> it easier to create the input models for BASEMENT (As Pete already wrote
> the Crayfish plugin to use QGIS as a Postprocessor for this Models). I
> hope that ETH will release their plugin as GPLed (though I am not sure
> now) and that work in this field will continue.
> 
> I already started a wiki page some time ago on this topic
> (http://hub.qgis.org/wiki/quantum-gis/Hydrology_and_Hydraulic_modelling)
> and it seems that a lot of people are either working or are at least
> interested in this topic.
> 
> As I still believe that you need something more simple for your solution
> I hope that probably someone else can jump in here and explain an easy
> way to just do sinkfilling in small rivers (maybe r.hazard.flood is
> enough for you?) but personally I have not seen such an (easy) tool. But
> as already said, it depens on how reliable you would like to have the
> results. If it exists I would also be interested howto use it.
> 
> For the other programs you can always come and ask me howto do it but be
> warned that creating such an input model is really time consuming.
> 
> Hope that answers at least some parts of your question. (And I know that
> you'll surely find a lot more on the given WIKI Page - thanks to all
> contributors to the page!)
> 
> kind regards
> Werner
> 
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