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How are polygons (building) represented on a grid?

Posted 28/07/2019 15:06 by JAlton

Last post 31/07/2019 10:52

2 replies


Im increasing roughness of building footprints to represent them. I am wondering how they are 'cut out' of the grid.

For example.

1.  A cell is cut from the grid if any part of the cell is covered by a building.

2. A cell is cut from the grid only if the entirety of the cell is covered by a building.

3. A cell is cut from the grid if the centroid of the cell is covered by a building.


these are examples which i have seen in other flood modelling softwares, but i cannot find any information on the topic about flood modeller.

Thanks, josh

Issue loading .tif in v4.5

Posted 12/07/2019 11:03 by A FloodModeller

Last post 12/07/2019 15:57

1 reply


I'm having issues loading an open source raster map into Flood Modeller v4.5. This loaded as I expected in v4.4. Since upgrading to v4.5, loading the geotiff seems to apply a blue colour ramp that I don't want. Is there a way I can load this without the colour ramp being applied?

Thanks in advance! 

Unexpected results from setting buildings to a roughness of 1 (mannings) via shapefile.

Posted 11/07/2019 15:21 by JAlton

Last post 14/07/2019 10:46

3 replies

Hi, im running flood modeller with both ADI and TVD 2d solutions for a catchment (google map of the catchment). Keeping the model simplistic i am using a user entered rainfall and a global roughness. The only difference between the model runs is the addition of a shapefile of all buildings with an associated roughness of 1 (mannings).

Results when using roughness values of 1 for buildings: lower flood depths for roads besides buildings and higher flood depths for areas where the buildings are. This is in comparison to a simulation not representing buildings in anyway. I would assume that the opposite would happen with higher flood depths being modelled when increasing friction for buildings. Is there any reason why this may be?


thanks, josh

How are buildings represented in flood modeller free?

Posted 20/05/2019 21:21 by JAlton

Last post 21/05/2019 13:21

1 reply

Ive looked for infomation regarding how buldings are represented within flood modeller free, ive read that water flows around buildings and assume that it takes the 'stubby building' approach by increasing the boundary of a building by a certain amount. However, I cannot find any technical infomation or infomation atall about the process flood modeller takes. Any sources to infomation would be greatly appreciated.


Thanks, Josh

Website down for maintenance

Posted 02/06/2017 15:23 by Joe Clarke

No replies yet

As you have hopefully already seen in the recent Flood Modeller newsletter, floodmodeller.com will be down for maintenance from 6pm BST today (Friday 2nd June) until 8am on Tuesday. During that period, there will be no access to downloads, to the forums or to our online support system. Sorry for any inconvenience this may cause.

You can continue to contact our sales and support teams via email and telephone as normal.

ReFH2 Unit

Posted 05/12/2016 12:26 by cjh

Last post 07/12/2016 14:45

3 replies

Hi All,


Slightly frustrated this morning as it appears the introduction of the ReFH2 unit now means that we must have ReFH2 installed on every machine which we need to run a model (using that unit)on!  Am I missing something or is this really the case? The unit only appears to generate the hydrograph at the time of running the simulation, thereby requiring each machine to have a license to run a ReFH2 simulation.  

We've paid to be able to generate hydrographs, must we now also pay for every modelling machine to run the simulations? Or hopefully, I have missed something.

Landslides into rivers

Posted 02/11/2016 09:09 by fiona

Last post 02/11/2016 12:47

1 reply

Any suggestions about how to model a landslide into a river?  We are looking at an area where local residents believe that the sudden failure of a a length of river bank (very approximately 100m x8m high x 5m wide) during a flood event, led to overtopping and subsequent rapid failure of embankments on the other bank leading to significant property flooding.  There are obviouly other mechanisms by which this could have happened, but I'm curious if anyone has any suggestions of how to assess this, other than the obvious, that if the model calibrates without a sudden failure we don't need to look for other factors.

UK Design Rainfall Profiles - differences between FloodModeller and ReFH2?

Posted 29/09/2016 11:10 by maspiers

Last post 29/09/2016 17:04

3 replies

We've found that we get different rainfall profiles depending on whether these are produced in FloodModeller (say, using an ReFH boundary) or in other software (InfoWorks ICM and ReFH2). 

This graph comapres the results for 1:5yr 1hr summer event, scaled to give a total rainfall of 1, for profiles from InfoWorks ICm, FloodModeller using a ReFH boundary unit, ReFH2 using FEH99 parameters and ReFH2 using FEH13 parameters.


Anyone have any idea why these are different?

Flood Modeller for A Level Geography Students

Posted 24/06/2015 14:19 by David_Morgan_FSC

Last post 24/06/2015 15:55

1 reply

I am looking at the possibility of using Flood Modeller to create models which could be used with A Level Geography Students. 


The Exam requirements for A Level Geography are changing next year, to a more Systems based, whole catchment based approach to rivers, as opposed to simple changes along a rivers course. As fieldwork, students would look at a small catchment and consider inputs, transfers, stores and outputs to that system and resultant issues, including flooding.

They will take measurements of the river channel, including calculations of mannings n, and consider impacts of inputs on maximum flow.

I would like to create a simple model, max 5km of channel length, and around 10 cross sections, to explore the flood risks within that small catchment.

Not being a modeller i dont know much about doing that, i have seen isis in use before and think it could do that - but some words of wisdom and pointers to help would be VERY welcome.

Many Thanks 

David Morgan

Field Studies Council

Welcome to the Flood Modeller forum!

Posted 30/04/2015 17:16 by Joe Clarke

No replies yet

To coincide with the launch of Flood Modeller, we have set up the Flood Modeller forum. It's a great place to pose questions to and learn from other members of the Flood Modeller community.

We have also launched a new YouTube channel, with some great 'getting started' videos, with more content being added all the time.

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