What Bengaluru needs now: flood zone maps to help buyers

t's not easy to navigate between loads of documents and see whether there is a violation in the property that you buy. Bengaluru needs to identify its flood zones to prevent future financial loss to the inhabitants.

Google Earth image from 2000 that shows a realistic view of elevation and valley in Kodichikkanahalli area.

Recent actions by the government to clear the drainage encroachments in the IT city have proved to be a tough incident both for the administration and to the individuals. Though people getting their plans approved or Khata documents can be attributed to the dark side of the administration as well as of the individual dweller, there are certain genuine innocent cases that are heart-breaking.

In the city considered to be IT capital of the country, where a normal cab driver reaches a completely unknown destination using a simple search in his smartphone, it is a pity that even so-called technically empowered professional of an IT firm is unable to figure out whether the location of the property he is planning to buy is an encroachment of lakebed or a drainage. That too, after spending months on research and consultation with real estate experts and lawyers.

Now that’s a paradox. On one side we have the locational intelligence to the extent of navigating meter to meter that hardly consumes any time. On the other, even after researching for months together we fail to determine if a location falls within any specific zone. On the contrary we hear officials saying everyone must refer age old village maps before buying. Where did we go wrong?

In United States, which is highly prone for flooding disasters, for housing loan and construction purposes, it is mandatory that you obtain a certificate that specifies if the location of construction is within or outside the flood zone. In USA, the entire nation is divided into 500 years flood plain, 100 years floodplain and no floodplain. Depending on which zone the construction falls, the flood insurance is mandated and the premium is decided. Looks wow, but there is nothing special and similar project to decide encroachments is quite doable here as well.

Are we capable?

In fact we have already carried out better projects. BBMP has GIS maps with individual PIDs (Property IDs) for tax collection purpose. Here in this case, they have mapped each and every land parcel. This is quite time-consuming and tedious job. Coming up with flood-zoning maps is far simpler compared to GIS maps for individual PIDs. I am not really sure if the GIS maps for individual land parcels has helped in collecting taxes, but zoning maps will surely help in checking encroachment, corruption, confusion, cheating and eventually the unwanted incidents like demolition.

What do we have now?

Clearvalue.in is a website that has Bangalore CDP map overlaid on the satellite image. In the opening page one can select the area where the property lies and with an approximate idea of the location navigate to the area of interest and see in which zone of CDP the property lies. This gives a fair idea on if the property is likely to be in the danger zone. If the property is residential or mixed residential, yellow zone, with no green-coloured valley zone or storm water drains in between, the property is technically supposed to be safe.

This will give an idea on the zone in which the property is likely to fall. The overlaying on Clearvalue website is fairly accurate in the central part of the city and the accuracy fades as we move outside. Hence we can’t take this as a tool to decide on buying a property. Hard copies of CDP will also be of not much use.

CDP is a comprehensive map of land use and land cover of an area, but many of the existing issues are not covered in the map. Also, we can’t locate the property using the coordinates (latitude and longitude) of the property. This website is not authenticated by any government authority. The zoning can be checked by going to Drushti section of BDA website, however this section is offline most of the times.

Is this fool proof?

Absolutely not. The valley zones that are supposed to indicate flood zones in the CDP map are based on old village maps, but in reality many drains and lakes have been encroached and the topography of land changed. The CDP doesn’t account for the realities caused by corruption and compulsion in the system.

A realistic view of flooding zones

What we need is a realistic view of the land and flooding. Primarily we need a GIS map of all the villages falling under the boundary of interest. A geo-referenced and mosaicked images of the villages can be used to digitise all the relevant features and also to classify them into different zones like government land, Rajakaluve, lake bed, public area etc. A zone where it is deemed that the construction is legal may be created for the easy understanding of the common man. Extreme care must be taken to ensure the accuracy of the maps.

Once this map is prepared, the existing GIS map of individual land parcels can be overlaid on this. Finally this combined maps can be overlaid on the satellite imagery for better visualisation. Transparency level of each layer must be allowed to be set by the user so that, it can be adjusted accordingly to be able to see the layer beneath.

Once the project goes live, the user should be able to locate the property by

  • Navigating to the location by visual references
  • By entering the latitude and longitude of the property, which he can obtain by going to the site location using a smartphone (This would be the fool proof method of locating the property)

If the property searched is falling within the zone where construction is legal in all means, the user can proceed to next step towards the purchase. If it is falling in other zones, where construction can’t be permitted, it’s a straight inference on the negative side. (Of course most of the constructions in east Bangalore would fall in red zone). This reduces the risk of the individual buyer that much. As the project would be carried out and approved by the government, officials or representatives will not be able to give any excuse on errors.

Do we have the expertise?

Very much. The government nodal agency for Remote Sensing and GIS, KSRSAC (Karnataka State Remote Sensing Application Centre) has proved its credentials beyond doubt, by successfully carrying out projects like LRIS (Land Resource Information System). Remote Sensing Centres of many states were waiting for the outcome of this project to carryout similar projects in their respective states. KSRSAC has set precedent in many such projects, which were far more complicate than the one we are talking about.

Budget and time consumed to complete the project would surely be less compared to the project of mapping individual land parcels.

Once complete and live, yes, an individual will be able use the locational intelligence to find if the property is genuine or encroached, as easily as he uses the locational intelligence for navigation in his smartphone. This is what this city and citizens need now, to prevent further disasters.


  1. Sreenivasan A V says:

    What are the various ” Khathas” like “A” Khatha, “B” Khatha etc. Where are they defined. Who issues them. What are the requirements to issue these documents and what are the purposes of holding these documents. Can any one clarify with reference to Municipalities acts prevailing.

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