We use cookies to make your experience of our website better. You can delete or block cookies, but some parts of this website won't work without them. By using this website you accept our use of cookies.


15/06/2019 22:12:11


I am trying to use a mastermap greenarea shape file for roughness in a 2d simulation. Currently, im running into a problem when i try and start the simulation: "WARNING: multi-part polygons present in file (path to shp file) - these are not fully supported..."

So far i have:

edited the original shp file to include a column called "DescGroup" with descriptions for each row e.g. grassland.

Created a .fric text file with the descriptions from the shp file and roughness coefficients.


Thanks for your time, Josh


17/06/2019 09:11:11

Best answer

Mastermap layers will often contain features which have multiple (separate) parts or have holes in some of them. EG in QGIS you will need to use 'multipart to singlepart' and 'delete holes' tools to generate layers which do not have this type of geometry before FMP will accept them. Good luck 


17/06/2019 13:21:25


Thanks for the response Nigel,

Ive done what you suggested. The simulation is still not running and is saying 'info - starting mastermap read' (been about 10 minutes).

I am using Flood Modeller Free if that changes anything.



17/06/2019 13:45:33

Perhaps there are other issues with your modified SHP? Perhaps simplifying the file with reduced geometries and reintroducing feautes step byt step would help diagnose the problem with the file.


18/06/2019 23:23:47

Ive done that to no avail, i have just split the main landuse types into seperate shapefiles instead. Id still like to use mastermap roughness though. I think it may be a problem with my lookup table. Am i right in thinking it is simply a text file saved as '.fric' and is set out like:

building 1.000

field 0.100



19/06/2019 09:16:57

With the .fric file, from memory, the number needs to begin on column 41 of each row. I.e. the first 40 characters are for the name, bulked out by spaces:

Buildings                               0.3


19/06/2019 15:29:04

Success! It was my fric file, thanks for all your help Nigel, much appreciated


19/06/2019 15:35:43

No worries, glad to be of help.

Sign in to create or reply to forum posts.

Privacy & Terms