plausibility questions

[foproy]

i am looking at running a game soon that will be a take on the old Freeport series set in a campaign setting i am working on. Basically the idea is a post apocalyptic world and was wondering how plausible it would be for Shreveport to be a hidden port should New Orleans flood. most of Louisiana is below sea level.

[MilitiaJim]

Pretty plausible, depending on your sea level rise.  Shreveport is currently 177 feet above sea level, and New Orleans is 10 feet below.  Alexandria, LA is about 75' up, and Baton Rouge is 60' above sea level.  The trouble with Shreveport is that it is not on the Mississippi.  Natchez or Vicksburg might also work.

Regarding Texas:  Houston is 43', Dallas 400', San Antonio 700'.

[foproy]

looking at maps i see a couple of lakes near the area could extend the city into a hidden port for sailors who really know the waters outside of the area. which would make it good for the story of the module.

[Blankbeard]

Here's a relief map of the state.  If you put "relief map louisiana" into google maps it'll come up with one that includes cities.  City elevation estimates seem to vary from 144ft to 258ft.  Depending on how much water you put on the state, Shreveport should be at the end of a long potentially treacherous inlet, maybe 80 miles long and 2-5 miles wide.  Assuming of course that your apocalypse doesn't do much remodeling of the land.

Here's another map that let's you see the flooding by various sea level increases.  It looks like it takes 40-50 m of water to get where you need it.

As to how hidden it is, I can't say.

[foproy]

what about the rise caused the state to flood, but overtime when most of the rest of the water receded the area became an inland sea? looks like that is not too implausible.

[Blankbeard]

I am certainly no expert, but it looks like the land SE of Shreveport is all lower and the land NW is all higher.  So some lakes might expand but I don't think you'd end up with an inland sea without remodeling the land.

[foproy]

or am i just putting way to much thought into this for a game world?

[tfwfh]

According to the US Geological Survey, in 1992 Shreveport's elevation along the Red River was just about 150 feet.  Moving away from the river, elevation quickly climbs above 250 feet.  Even if sea levels rose 150 feet, which may not be possible, most of Shreveport would be minimally effected, and it would essentially become an area of narrow inlets, following the paths of existing rivers and streams.
http://www.lib.utexas.edu/maps/topo/louisiana/txu-pclmaps-topo-la-shreveport_east-1992.jpg, for reference.

I couldn't find anything for Alexandria, but I also didn't look very hard.

The lowest point in Baton Rouge are at a 20 foot elevation, the highest a little over 70 feet.
http://www.lib.utexas.edu/maps/topo/louisiana/txu-pclmaps-topo-la-baton_rouge_east-1995.jpg

At the end of the last ice age, the fastest that sea levels rose was about 1 foot per decade for a period of roughly 500 years.  I don't know much about this setting, but if you're concerned about real world plausibility, Shreveport is probably not going to become a coastal city.

[Blankbeard]

or am i just putting way to much thought into this for a game world?

I don't think you are.  If your players aren't that familiar with the area you're using, go ahead and put your inland sea there. 

My go-to for fantasy maps is Mesozoic America.  There are so many variations in shorelines.

[MilitiaJim]

With a bit of seismic fiddling you could make the Utah basin a sea again.

[foproy]

could a carpet bombing of new orleans and say sever old and angry gods escaping through ancient and severely weakened barriers cause sufficient seismic activity to cause the inland sea?

[MilitiaJim]

Meteor strikes Salina, KS, liberating the natural gas under the bedrock.  The entire region burns then sinks, (what, a thousand or two feet?) and the water flows in.  Throw in a couple more hitting the north Atlantic, and western China, and you can frag most of the world.

[tfwfh]

I think if there are old and angry gods involved, you can just go ahead and do whatever you want.

[foproy]

well i had some ideas. these are concurrent events and not 2 different ideas.
when the dead walked the earth.

when there is no room left in hell the dead shall walk the earth.

no one knows why this happened(well except me i have an idea involving them not actually being dead and instead a version of the rabies virus reducing people to base instinct. any survivors of this became the first orcs and goblins) but many recent dead began attacking people. many humans died dugin this time, and a lack of maintenance caused technology to shut down which lead to...
the day it rained fire
the sudden loss of power led to many of the worlds satellites orbits to decay and them to fall to earth. much of it was bashed to pieces during the fall and burned up mostly harmlessly but a lot also made landfall causing some changes to the landscape and sending many people running underground (these people eventually became dwarves). the other fantasy races came about as the strength of specific barriers maintained by different secret societies began to weaken and ancient and nearly forgotten things broke through (elves, drakes, pech, and fae).

[Desertpuma]

You could always use Miami or Tampa with water elevations another 20 - 50 feet higher to get what you need