What do you mean by "Urban", if you mean mix drainage of pressured pipe and open channels and street surfaces, I do not know of a single free software to do that.

ICM-Infoworks, XPFlood and Mike Flood can do that (all commercial)

You can use :

EPA SWMM, for pipe and simple channales (it is free), You can use HEC-RAS, SRH-2D, CCH2D and Iber for surface and channels in the city and they are all free. But you need to manually link the free surface flow and pressurized flow in those, which is a pain in the neck!

Hope it helps,

Kaveh

Dear Mukesh

Try using QGIS (qgis.org).

In this software there are some important algorithms of other software, all available for free and that can meet your demand.

Here are some:

TauDEM

GRASS

SAGA

These packages feature diverse applications to similar and automate processes over areas from DEM and other data such as precipitation, infiltration, slope etc.

Here are some interesting links to your research here:

https://plugins.bruy.me/processing-taudem.html

https://www.youtube.com/watch?v=liX1ysdUGCU

https://www.youtube.com/watch?v=PHWA_8doRyo

More details about qgis go to: qgis.org

See this article: https://www.mdpi.com/2076-3263/9/2/77/htm

See this question here from RG: https://www.researchgate.net/post/Methodology_to_generate_flood_risk_maps

Regards

Kaveh Zamani

In my study area there is no river and for inundation the only input parameter i have is rainfall data. So can I use HEC-RAS for my study

If only you are dealing with "free surface flow" in your area (no stormwater drainage pipeline) yes, you can use HEC-RAS. Make 2D mesh of your area in HEC-RAS and put your hydrologic hydrographs on that as external loading (input).

Dear Mukesh,

You can use HEC-RAS if your purpose is to model urban flood. Also, Open access DEM data can be retrieved from the Space Shuttle Radar Topography Mission (SRTM) and ASTER Global DEM available at https://earthexplorer.usgs.gov.

Mukesh M S

If you only have rainfall and terrain and soil type and land use, you have to use a hydrology software first (convert the rainfall to overland flow) then a hydraulic software (find the path of that overland flow). You have to use HEC-HMS fist to find the hydrograph of input for hydraulic model (HEC-RAS)

Dear Mukesh

I agree with Zakari that in terms of freeware HEC-RAS is probably the best and easiest software to use. You can set up a two dimensional grid of an urban area.

In terms of digital terrain model (DTM), in my opinion, there are no freely available DTMs that are sufficiently accurate or are based on a fine enough grid to be able to represent the complexities of the topography in urban areas and the effects that these can have on flood flows and depths. The ASTER DTM (and various others) are free but at the very best are based on a 30 x 30 m grid which is not sufficient in urban areas. Ideally you need a 1 x 1 m or even 0.5 x 0.5 m grid DTM.

The other challenges when carrying out surface water flooding in urban areas is that you'll need to make assumptions about:

• Net rainfall

• Runoff coefficients for different land uses within Dar es Salaam

To obtain the net rainfall the total rainfall will need to be modified to represent to allow for what is stored and conveyed in an urban area’s drainage systems. From experience in urban areas the drainage system ‘removes’ rainfall at a rate between 5 mm/hour and 15 mm/hour. This rate will depend on the capacity of the current surface water drainage system in the urban area you're modelling. It is best to carry out a sensitivity analysis using a range of "rainfall removal rates", to see what impact that this has on maximum surface flood water extents and depths. You'll also need to consider what runoff coefficients to use for different land uses as well as the effect of buildings on floodwater pathways.

i hope that this is of help.

Darren