Here's a compilation of my #maps which can help you in understanding the #Bengaluru #Water situation a bit better.

Bengaluru is unofficially a hill station which is located nearly a kilometre above sea level. Being in the top of a ridge line, the city is partly within Kaveri watershed and partly in Ponnaiyar (Dakshina Pinakini watershed).
Being on top, water from elsewhere dont flow through Bengaluru but flow outward from the city

Here is the story of how @googlemaps helped me recover items stolen in a moving train from my father.

My father was travelling from Nagercoil to Trichy in sleper class in Nagercoil - Kacheguda express. He had boarded at 1:43 AM from NCJ. The train was relatively empty & another person who boarded along with my dad stole my dad's bag and mobile phone from him, and deboarded the train in Tirunelveli Junction. When my dad realized it, he searched in the train and rang me from his friend's phone at 3:51 AM to inform that his phone was stolen. Luckily, among immediate family members we have location sharing "on" which meant I could track the location of mobile. When I checked it, I realized that the mobile was moving along the track near Melapalayam in Tirunelveli so I deduced that the thief was returning back to Nagercoil in another train.

Thread:
I'll summarise the #Chennai cyclone event and the flooding issue once again as I feel that there is a lot of misinformation floating around which could guide people and government in wrong way w.r.t future actions
#ChennaiFloods2023
1/n 1. The cyclone path had been more or less accurately predicted by IMD, private forecasters

2. The intensity of rainfall however was not clear as per official forecast though it was expected to be heavy, it was not indicated that it would be near record rainfall

Short thread:
#Chennai, lakes, and floods

I have written some threads about the flooding in Chennai, this one would focus specifically on the lake aspect.

#Map below shows the flood forecasted areas in Chennai for an extreme amount of rainfall. If we carefully look into this forecast map, we can see that apart from the major rivers, there are many other paths for the water to run which appear like a tree branching out.

This forecast based on coarser DEM with extreme rainfall & was prepared by my team mates @smkirthiga & pavithra

Pardon the visual quality of maps since I dont have much time to prepare this
If we look at the topography map, the flow paths become clearer as in the map below. When water falls in these places, they are supposed to drain along these streams which appear only during monsoons

Thread:
A recent #satellite image of the sea near #Chennai's Marina beach. There are 3 dots in the image (red, green, blue). What causes it? Satellites have cameras that observe reflection in different spectral bands (including red, green, blue). But they don't observe the same place at the same time and there is a very small lag between them. Meaning between red colour and green colour there is a time difference

#Thread: A Problem in the making. Two major problems faced by #Bengaluru are flooding and traiffic. But just like any other Indian city, unbridled urbanization is aggravating these crises and is making sure that these problems would stay for longer
1/n In my previous posts, I have explained about the topography and valley system in #Bengaluru. These conveyor belts carry the flood waters of the city. It is across these valleys small dams were built primarily for irrigation purpose (which we now call as lakes)
2/n

#Thread on Ponniyin Selvan #Maps
Last year, I had the opportunity to work as map consultant in director Maniratnam's magnum opus, #PonniyinSelvan movie. Though seen only in bg, there was a lot of professional effort put into maps which must be the 1st in Indian film industry 1/n Maps show the core Chola territory and the areas that were conquered and subdued.

2/n

Short #Thread: Does the #Cauvery river need another dam?

Kaveri river is one of the most exploited watersheds in the world and yet there are many calls from both Tamil Nadu and Karnataka public to build one more mega dam
1/n It raises from a myth that there are not enough dams/regulators in Kaveri.
But there are more than 28,000 artificial constructions across Kaveri & its tributaries as Dams,Weirs,Regulators so that water could be stored/diverted for consumption- Agri, Energy, drinking
2/n

#Thread

Another city, another neighbourhood, another stream but same story

This is about a nala that flows through the dense urban concrete jungle of #Hyderabad city. It flows through Padma colony of nallakunta neighbourhood and eventually joined Musi river. Like many streams and canals in urban environment in India, this stream also didnt have any buffer in case of severe floods and jailed with concrete walls and no room for it to breathe. For most of the year, these streams carry sewage water.

#Thread on Local Football

WorldCup is over. Though football has lost media attention in India,local football is living& thriving even under difficult situations

As my club is gearing up to organize a tourney, I'm writing this to show d love & troubles, d game faces
@Udhaystalin Contrary to perceptions & opinions, Football is quite popular in many places in India like my town (Nagercoil, Tamil Nadu). 300-500 people (mostly young) attend matches even when conducted during the peak of summer and during a working day. Photo taken during pre-match
2/n

I am yet to write all my suggestions related to the climate action plan for Chennai which has been open for suggestions

But wanted to say this:
Please DON'T take all these sea level rise maps from the report that depends on climate central. These are INCORRECT.
@chennaicorp What is wrong:
1. Elevation models used for these analyses are incorrect
2. climate changed induced sea level rise wouldn't act like a bath tub where water rises just like that
3. There would be formation of new beaches and erosion and would be different from current topography

#Bihar
1) Throughout the entire south west monsoon season, Bihar and the catchments of the rivers that flow through it have been facing deficit rainfall. But.. 2) Throughout the entire season, Kosi river has been flowing above warning level for every day and above danger level almost every day!

Isnt it odd that a river basin that is facing deficit and drought like situation have flood too simultaneously?

Short Story: 🧵

Near wonderla exit in #Bengaluru - Mysuru road, there existed a valley system (flow directions indicated below). Few irrigation tanks were also there in the valley (marked in blue).

1/n The construction spree on top of the valley system started when the road was expanded along with a toll gate right on top of valley! And other builtup came along the highway too completely causing the valley system to be obstructed.

2/n

Short #Thread:

Though heavy rainfall is the trigger, our construction practices of where and how are the biggest causes behind some of the most devastating landslides that are costing both lives and money for us.

1/n Image shows a relatively well vegetated hill slope in #Manipur in 2009
2/n

Short #Story of a river, a sea, a fishing village, and a groyne

Satellite image from 2005 shows the delta of Porunai river (Thamirabarani) in Thoothukudi district of Tamil Nadu.

1/n The river settled some amount of sand in the sea and close to the mouths the sea was shallower and with lots of sand.

2/n

#Thread:

#Visualization shows ownership of Cars, Bicyle, Two wheelers and also the households that dont own any of these

Why is this critical to know?

Prepared by @PratapVardhan @Stats_of_India
h/t @indiainpixels Before going into the thread, let us clarify about the data. The data is an end product of a survey which surveyed around ~6,40,000 households across India

Data represented in this viz are aggregated at state level so rural-urban or other geo nuances might be hidden

2/n

This is a bridge across the #Chambal river near Morena (on the Madhya Pradesh side of the river), massive sand mining operations are happening right below the bridge! So many bridges across India have collapsed because of this activity More images...

#Thread
Story with maps about Vaan Theevu, a small island off the coast of Thoothukudi, Tamil Nadu.

Animation shows how much the Island has changed over last 3 decades. It has been shrinking for a while.

Here's my take on the subject. Please do read this long thread!
1/n 2)Vaan is one of the many islands found off the coast in Gulf of Mannar. The island along with others are now protected areas.

Vaan island is in the shallow continental shelf part of sea. 3 islands existed to south of it but they were all merged/modified for construction of port

#Thread: Here are my views on use of satellite images & maps in the Economic survey 2022.

Overall I have a mixed feeling. I am so glad and delighted that a section has been devoted in this manner but I am not happy how certain maps have been presented as they tend to mislead One of the most highlighted map in the survey was that of night lights. It left many wondering whether India actually grew this way. The answer is no and yes. Night lights did increase over the longer period but it is way exaggerated in this map

To protect the borders in #Kanniyakumari District, Travancore kindgom under guidance of Capt. Eustachius De Lannoy built South Travancore lines - a series of fortifications in ~1740s between the ocean & mountains & are now in ruins after being overrun by Company troops in 1809 Except Vattakottai fort, all the other sections of the lines are present as bunds or demolished and now used as roads. Some ruins of the bastions and redoubts are still visible in some places.

Google Earth/Maxar Rendition of Vattakottai fort overlooking the sea.

India - State of #forest report from Forest Survey is out. If you get news articles (how forest covr increased/decreased), read it with caution. Will write detailed comments later, but some small fun for now:

In ch-13 maps, they have given Shaksgam away! Illegal to publish..
1/n They had some city level maps of forests.. And their statistics depended on boundary files and the file for Mumbai is riddled with gaps between subdivisions. There are white patches in between because someone didnt digitize it properly and these errors creep into stats