Infrastructure Infrastructure

Given the fact of Global Warming and the very large probability of significant future sea-level rise, it should be obvious that a number of coastal cities will have to be abandoned, which means their populations will need to move inland. Sounds like an excellent opportunity to plan some new cities, from the underground up.

Having selected some likely terrain, the city planners would decide where the main roads should go, and mark the ground accordingly. We now start digging them up, nice deep trenches, say 15 meters. All the trenches are thoroughly sealed against the water table, if present. We now put a roof over the bottom 4-meter space, with numerous suitable access points.

In that space, in the future (as buildings get built), we will put conduits for such things as sewer lines, water lines, power lines, gas lines, communications lines, and so on. The conduits should be sealed so that the remaining space can double as a storm-drain system. Note that when the storm water is pumped out, it could be filtered and considered part of the city's overall water-reservoir system. The conduits should also be organized such that appropriately designed service vehicles can drive through these pathways, so service personnel can easily reach specific locations for such things as installing connection points for future customers.

In the space above that level, we plan for a subway/metro transport system. We don't need to think about actually putting such a system in there until the population of the city is large enough to need it, but having the space ready in advance, to prevent major traffic interruptions that happen in any ordinary unplanned city, is a good idea.

Also, like the London Underground in WW2, this level might be suited for emergency sheltering of the population.

Above the transport level we have another roof, this one heavy-duty enough to support the dirt that we will put back into the trench, plus the roadway that will eventually be built, plus all the vehicles that will eventually occupy that roadway. Likely, to be strong enough to resist that, it will also be strong enough to resist the atmospheric overpressure associated with an air-burst nuclear explosion (see above about sheltering the population).

As buildings get built, relatively small/short trenches or tunnels need to be dug to connect to the main Infrastructure Infrastructure tunnel system.