Tokyo's Underground Discharge Channel (opens in new tab)

I've been following the Chicago Deep Tunnel project, which is nearing completion after half a century of work.[1] Because Chicago was built on swampland and next to the lake, rainwater used to be a huge problem because it didn't have anywhere to go when it rains, except into sewers - which used to be well under capacity for burst rainfall, which led to basement flooding etc.

So the city is building (and almost finished with) a set of huge tunnels across the entire city that regular sewers will drain into during flash floods, and then pump the water out to reservoirs repurposed from abandoned quarries on the edge of town. The target capacity is 17 billion gallons, which is apparently the volume of twelve football stadiums stacked together? [2]

I'd love to tour that construction. Not sure they offer public tours though. :)

[1] https://interestingengineering.com/chicagos-deep-tunnel-proj... [2] https://www.mwrd.org/irj/portal/anonymous?NavigationTarget=n...

There is a software for modelling drainage systems called SWMM (Stormwater Management Model) that has been around since 1970s (!) and is programmed in C and released as free software. Still most modern drainage and sewer research is modelled via this software and there are several companies that built a GUI for simpler usage. However the core is often still based on this nearly 50 year old software which I find amazing [edit: it has been updated since then and originally it was written in Fortran].

The model has hydraulics and hydrology capabilities [0], i.e. it can model stuff like pipe pressure but also takes infiltration of stormwater (aka "rain") into the surface into account. When using it you have to define your sewer (which is mostly a directed graph) and so called catchments where you define which areas drain into which nodes (inlets) by defining parameters like impervious area, slope, etc. You can then let it rain on your area of interest (e.g. a city) and find out which nodes get flooded at specific points in time (or hopefully not).

[0] https://en.wikipedia.org/wiki/Storm_Water_Management_Model#H...

Note: it's about 1.5 hrs (each way) from Tokyo, and you need someone in your group who can speak Japanese.

Reservations here: https://reserva.be/guidetour

http://www.bbc.com/future/story/20181129-the-underground-cat...

Wow, I hope the grid can handle the relatively sudden appearance of 780 MW of load. I assume they have some protocol in which why turn on one pump at a time and coordinate with the grid operators.

Flash flooding is a thing. In Hong Kong, the Drainage Services Department puts up warnings and runs TV ads to tell people to stay clear of discharge channels, lest they get swept away by flash flooding during heavy rains.

So if intake into the discharge channel is not controlled, isn't it kinda dangerous to film there?

Tokyo was built on an estuary so the canals came from the management of the water that was already there. The final evolution being the water being pushed completely underground is pretty predictable. Other cities have dealt a similar fate to their rivers, London being a prime example where only the Thames is really 'welcomed' as a river, everything else is kind of banished underground.