I'm trying to create a Coruscant type planet with massive cities. Any specific way to stop overcrowding? There's always long lines of traffic and millions of civilians walking all over the place. Any way to evenly distribute the civilian population so that it is not extremely crowded in 1 place?
For Arbitrary Population Size
If you want a solution for any arbitrary k, where k is the size of the total planetary population, it cannot be done.
All fixed resources have their hard limits. This includes planetary surface area and total planet volume. For sufficiently large k, there comes a point where both resources are exhausted and the planet must be vacated.
The only way out is to impose:
- A hard population limit, enforced through legal/punitive measures.
- Offshoring requirements for overabundant populations via forced relocation to satellite systems.
- Zoning requirements that impose a hard limit on the number of residents within their premises, which, if enforced, will prevent immigration once Coruscant reaches capacity.
- Strict temporary visa allotments that prevent overstay longer than a minimum sufficient period.
All of this serves to cap your total population size to a sustainable number, and does not let your planet's support system scale indefinitely.
For Fixed Stable Population Size
Assume now that you only want to be able to support a total population of k, and are willing to exact measures to prevent excess above this. We will proceed on the premise that a stable population has been produced i.e. the birth rate exactly equals the death rate, and your planet's overall population is at an equilibrium.
In order to prevent regional overcrowding, you must first consider the following natural limitations:
Extent of temperate regions on the planet. Assuming your population can only thrive in certain specific conditions, the range of latitudes that lets your population survive greatly affects population distributions.
On Earth, the vast majority of the population - 88%, to be exact - is concentrated within a fairly narrow bound in the northern hemisphere, with over half living above 27 degrees N. This coincides near perfectly with the North Temperate Zone, with an average temperature of 31 degrees Celsius and precipitation of 81 cm.
No one wants to live in unusually harsh conditions, so migration to/from the frigid or excessively hot regions of your planet is limited, assuming an alien physiology similar to that of humans. Since you're modelling your planet after Coruscant, which features an influx of migrants of all sorts of physiological proportions, I presume you cannot make assumptions about your alien physiology just yet, so you have to keep in mind the geography of your world before committing to a plausible solution.
Natural disaster frequency: Regions that suffer from regular natural disasters, such as hurricanes, active volcano eruptions, etc., historically strongly affect populations, precipitating a brain drain that leads to migration elsewhere. Catastrophic once-in-a-lifetime events can exact extraordinary economic costs, all of which alter the shape of population distribution in the short term and may be hard to recover from in the long-term.
Even a planet like Coruscant is bound to suffer from natural disasters. Obviously, the sort of disaster depends strongly on the nature of the planet and its orbiting system itself: a planet without axial rotation has no day-night cycle and suffers from uneven heating leading to different natural disaster intensities, while a planet with no ozone layer orbiting a yellow star will suffer from radiation leaks.
Resource distribution: A region unable to provide food, shelter, or security for its folks is not going to keep them for long. This ties in somewhat with the point about temperate zones, which typically come bundled with sufficient necessary resources such as food and water, but isn't necessarily connected to them. Some temperate regions may be stripped of vital resources, making them less self-sufficient in their own needs, which in turn exacts a living cost on its inhabitants that may or may not prompt migration. What constitutes a vital resource varies by region and by technology: the abundance of coal, for example, affects how likely a Victorian-era society will be to survive the winter, while coal in a purely geothermal society is no longer as relevant.
You also need to consider the following non-natural limitations:
Economic imperative: The chief reason migration occurs is because of better economic prospects. This is often tied to the resource distribution issue, but not necessarily so: government capitals can and do become urban hubs despite not being located on, for example, a river. On planets that have moved to a currency system and engage in economic systems similar to humans, we may safely assume that economic imperative is sufficient to prompt migration.
I'm going to use economic imperative as a catch-all term for a lot of different things here: tax benefits, industry concentration, and geographic closeness to place of work. These are all economic imperatives from a migrant's perspective, and so it seems to fit.
Economic imperative can be balanced out by considering cost of living. Urban hubs exhibit higher costs of living than rural population centers, so migration between locations is unlikely to occur if the difference between net take-home pay (pay after taxes) and cost of living is identical or less than the migrant's original home. I say unlikely but not improbable: long-term considerations, such as future career prospects, also matter.
Supply chain infrastructure: This is the flip side of economic imperative, and affects cost of living. Specifically, by supply chain infrastructure, I refer to how particular locations solve the problem of resource distribution and allocation. Geographically isolated regions (yes, this is possible even on a Coruscant-like planet: imagine a hub with fewer connections to every other hub than its neighbours) with poor natural resources have to import food and resources, which is more expensive than local home-grown provisions. Poor infrastructure or administrative overhead - say, an electric grid built from obsolete parts or unable to make headway through connections - pushes long-term costs on people.
Any effort to stabilise migration so that population distribution is effectively a constant everywhere must therefore address all of these concerns.
Finally, there is one last concern to take care of:
The nature of your government.
A nanny state would solve all these problems in a completely different way than a democratic state. Likewise, administrative decentralisation (say, each node in Coruscant has its own municipal authority) would prompt different solutions than a centralised authority. A state that advocates free trade over government intervention would expect solutions to come from there. You'll have to play around and mix-and-match with what suits your story best.
Take care of geographical inequities first. A city-planet like Coruscant has only way of doing this: massive terraforming.
The eviction of trees and plant-life in favour of concrete may or may not cause a runaway greenhouse effect - therefore, Coruscant must build its own equivalents to regulate its atmosphere. This helps nicely in preventing air-related natural disasters as well. Oceans, rivers, gulfs, streams, etc. may also be drained and replaced in favour of concrete. Coruscant drones also dig deep underground and construct their own synthetic mantle and crust, designed to never shift (preventing earthquakes) and allowing full utilisation of the planet's geothermal energy (assuming an Earth-like molten core). As a neat bonus, we can assume all suitable waste is recycled into the planet's core, providing a near-constant supply of indefinite power.
At this stage, no single region has more resources than any other. Power is centrally managed and distributed to the planet as a whole. With the mantle and crust stripped, living space as fraction of planet percentage has quintupled (say) and all mineral resources are now in the hands of a central authority. With an artificial atmosphere, it is now possible to strictly regulate air-related incidents as well. We have removed the geographic incentive for migration anywhere: every point on the planet is now exactly identical, with no temperate differences or resource differences and natural disasters now tightly controlled.
Now you must ask: with all this massive terraforming removing geographic inequities, it now poses a major supply problem: where do vital resources -like food and water - come from? Answer: it must all be outsourced, shipped to the planet. This brings us to the next part of the answer:
Understand your demographics, and distribute resources accordingly.
Coruscant's problem is that it must support any incoming type of alien, while maximising living space without giving up vital industrial processes (such as power generation). Your aliens may survive strictly on a diet of bugs that have to be imported from a different galaxy altogether, for example, but also want to live in a specific region close to their preferred industry. This means that every point in your city must be able to provide for a possible potentiality.
How your government chooses to handle the resource allocation problem is upto you: if your government is totalitarian, it may simply impose strict controls on migration and forbid people from moving there, monitoring their movements. If your government encourages laissez-faire trade, let corporations bid for the right to handle food distribution for an entire sector - aliens who require a certain set of resources will simply have to make the tough decision to move but afford their own private care.
Either way, your government has to import all of its vital resources from off the planet, since it no longer has any of its own. How it then solves the resource allocation problem depends on your government's strategy. I would also recommend enforcing zoning laws that prevent an excess of people living in a residential area, and I'd even go one step further in banning industrial activity on Coruscant's surface.
Tackle economic imperative. In a landscape of corporations, a particularly large corporation may want all of its employees geographically concentrated in one location. This in turn prompts more people to migrate towards a particular hub, leaving other hubs comparatively impoverished.
Fighting this is a difficult problem, but certainly one way to do it is to organise city architecture better. Instead of designing one massive city with roads and blocks - all of which causes extreme interdependence on each other and has a lot of moving parts - it's much better to break your city up into distinct, self-sufficient municipal regions. I envision giant geodesic domes actually physically demarcating boundaries.
This break-up into zones allows better regulation of industry growth: companies that seek to expand past a certain headcount must apply for separate offices in blocks that are not physically adjacent. This helps regulate population distribution simply by spreading out employees over the entire planet, preventing any single corporation from gaining geographical prominence. Corporations here include universities, research institutes, etc. - any organisation so to speak.
As a side benefit, this self-sufficient block design also pretty much guarantees that emergency services can respond quickly and are able to address the needs of its inhabitants, because each block would ideally have its own hospital, school, etc.
For a Non-stable Population
In addition to the previous list of issues, non-stable populations have their own additional problems:
Uneven age distributions: A population with more old people than young requires a different division of resources than a population with the inverse distribution. More old age homes and hospitals, for example.
Familial considerations: Migration can also be affected by intangibles such as perceptions of better school systems or hospital resources, which, for a non-stable population, can prompt major moves (although utilising a block-by-block system with corporations prevented from choosing adjacent regions can help mitigate this somewhat).
Solving both of these is tricky, and hard, and never guaranteed to work. I will point out though that:
- Encouraging the virtualisation of intangible resources is a good first step. Hospitals that admit virtual tele-screened appointments from anywhere across the planet means people can get the same quality of care from all over the world. Likewise, schools that subscribe to MOOC-like patterns are able to provide their content all over the planet, improving their own revenue while preventing major population shifts.
That's all I can say would work for your cause right now.