I always thought the Stargate in the show was ludicrously underutilized. They don't use it for anything!
First of all, we would never ever tie up the Earth's Stargate by running a military exploration program through it. Hell, it's not even remotely secure. We'd establish a military base off-world and run the entire exploration program through that. That way nobody would really care if the military base had to use the nuclear self-destruct option. Hmm too bad, we'll need to build a new base.
Opening the Choke
Secondly, the Earth's Stargate would be dedicated to colonization and resource (wood, iron, petrol, grain, and fish) transport. And the way you would run the Stargate is not using trains or cars or pedestrians, which would be immensely stupid. Rather you would place the gate horizontally so that gravity helped you drop things into the sending gate and out of the receiving gate.
Check this out.
(((pi * ((3 m)^2)) * (10 m)) per second) * (1 year) = 8.92251061 × 10^9 m^3
That's 9 billion cubic meters that can flow through the Stargate each and every year. And that's on slow speed because all you have to do is set up a funnel on the sending gate shaped in such a way that what's falling through is in free fall for one second.
In order to maintain a steady flow through the funnel, you'd set up the gate so it was movable, so you would move it away from the funnel as soon as it shut down so you could restart it. That way the kawoosh doesn't disintegrate part of the stream of goods you're trying to send. Then when it's online you slide it right back into the stream of (wood, iron, petrol, grain, and fish).
Changing Land Usage
To grasp what impact this would have on Earth, consider the world annual fish production of 120 million tonnes. It would take ((120 million tonnes) / ((721 kg) per (cubic meter))) / (9 billion (cubic meters)) = 0.018492834 (1.8%) of the Stargate's capacity to pass this through.
The world's telecommunications companies would rejoice since they would no longer have to put up with asshole fishermen cutting their (meticulously mapped) expensive fiber optic cables. And it would be much easier to regulate off-world fisheries to prevent destruction of seabeds since they would be utterly dependent on the Stargate to get fishing boats and nets off-world, and their catch to market.
Or consider the world annual roundwood production of 3.3 billion cubic meters in 2003. That wouldn't take up half of the Stargate's capacity. That's right, we could more or less end all forestry on Earth if we had a Stargate and didn't waste it like the dumbfucks at Stargate Command. And as a bonus, only the very best hardwoods would be harvested and sent through. But they would still be cheap.
Or consider the world's total cereal production of 2000 million tonnes. So (2000 million tonnes) / ((770 kg) per (cubic meter)) = 2.5974026 × 10^9 m^3. That wouldn't take up a third of the capacity.
When you add it all up, there's still plenty of room for the world's iron ore production (1.7 billion metric tonnes) / ((2500 kg) per (cubic meter)) = 680 million m^3.
Within 5 years you would displace 90% of the agricultural land usage on Earth, leaving the Earth's agricultural land for non-transportable fruits, vegetables and nuts. Hmm, nuts are transportable ... There would be massive reforesting.
And why would you do this? Well, maybe to capture some of the over one trillion euros per year that would be flowing through the Stargate. And that's at slow speed.
You'd think that passengers would be different. Well, they're not. Oh you can do things the dumb way by constructing custom trains and rolling them through the Stargate at a tempo of 40 per hour. That might get you up to 700 million trips per year. That would be dumb. And at 1000 euro per trip, that's only 700 billion per year of revenue. At 10,000 per passenger-seat, you won't find many takers.
But like I said, that would be dumb. The right way to send passengers through the Stargate is to fluidize them. Or better yet, to think of them as logs. Your job is to dump them vertically with the smallest cross-section possible through the Stargate and then into a lake of water. So it's wet suits and mini air respirators for the passengers. On the other hand, you achieve a throughput of
(pi*(300 cm radius of stargate)^2 / (pi*(50 cm width of shoulders of average man)^2 ) * 90% (the packing efficiency of circles on a plane) per second * 1 year = 4 billion trips per year.
Note that the receiving Stargates can be on any off-Earth planet. Because once you're off-Earth, efficiency no longer matters and you can just walk through your local gate to your final destination. You just need to make sure that Earth doesn't send all the passengers to a single planet - dividing them among 10 planets ought to do it.
So the way you fluidize passengers is you build a tube system. At each Stargate you build 127 tubes going into or out of each Stargate. Each tube starts at a funnel which accepts standing passengers on little platforms. Once the passengers are in their wet suits and respirators and masks, they step on this little platform inside the funnel. Then when the Stargates are working and the tube systems are aligned, the passengers are dropped sequentially 1 pax per second into the tube. They're going pretty fast so they've got 8 meters of headway between them.
Inside the tube you're dragged along by the water and the air is steadily filtered out. Then your tube starts to turn around so that it joins up with all the other 126 tubes into this huge bundle. And it's this straight bundle of tubes that's aimed at the event horizon of the Stargate. So you shoot down through your tube for a minute or two then through the wormhole then into a precisely aligned tube on the receiving Stargate. At which point the tubes are unbundled, twisted around so all 127 are in a single row and everyone's dumped into a fast-flowing but deep river. An artificial river that's flowing through pipes drilled through a gently rising smooth rockface right in the river. So you get scooped along upwards onto bare rock and the water you're in gets sucked into the rock, leaving you high and dry.
And that's how you send 4 billion people a year through a 3 meter radius choke point. As a bonus, you're providing an exciting and novel experience that nets you a few trillion Euros a year, every year. If you only use 25% of the Stargate's transport capacity for passengers then you can still offer 1 billion trips per year (more than you could offer with custom trains using up 100% of capacity) while leaving enough capacity free to transport all of the wood, all of the fish, all of the iron, and all of the grain the Earth needs.