Sinking Cities Plot Ideas

They have levies controlling the flow of water in and out of the swamp areas, - these are kept under conrol by magic, which was easier to maintain thanks to the salt mines on the outer rim of the swamplands - in case of heavy flooding/storms - the mines would take in the excess water and the main bayou would be affected by small tides of a few feet.
When the mines get full of water due to excessive water/levie breaks the rises would be closer to 10 - 20ft rises, those who were originally close to the waterline would either have to get to higher ground, abondon their homes, or unmoor their ships and let the silt/waves take them.
When the river south out of the swamp was constructed as a way to let out excess, it was thought to be a solution/to drain the swamp - but cause of the balancing act and amount of silt and detris the slow running "lying" river doesn't get much action until the wet season when it takes the excess.
Why this is important: Due to the mages who use to keep control of the levies death (cause of the Apocalypse along hording of knowledge) and their falting magics falling on the salt mines as their back up, the flood has only gotten more and more noticeable, where it would be low and high tide of a few inches, has slowly grown to feet.
The failure of a levie was imminent and the high council had advised the capitol to get prepped for a heavy flood season, but the people who are more able to ride out the season are those with estates on the floating part of the city (the central circle and the outer docks.) so they ignored the call and did not advise the others - only saying that it was another "seasonal" flood.
Those whose homes are on the stilts and stone basin built around the circle are more of the low tide/labor class who are pushed to work during the oncoming onslaught.
Where you come in:
The adventuring party are sent in to make sure a noble's home in the central circle, is up and running and clear of any issues during the onslaught. They do not want any of the riffraff (trying to survive the flood) to be on their doorstep or taking up room in their home. - The party has been hired to "infiltrate" the city that is on flood watch and ride out the disaster in the manse, when the flood water clears they are to make sure it is "safe" for their employers. They are to be paid on completion.
In short: Get in, make it safe, wait for it to be over, get paid.
Interest Gauge - Short Form Campaign (expectant 7 games, pending on how quickly you solve/burn down/sink the city) -
Location:
Online (but for finale in person host)) -  
Start Date: January 14/21st -  
Story: "The Day The Levee's Broke" a Sinking City
Summary:
You're merc who got hired for two jobs, get into the capital and protect the Silverscale estate. The only problem is the city is quickly falling into chaos and that's just normal flood season. The central and upper cities are on high alert and lockdown, the contract says that once you get to the estate everything wil lbe taken care of, but they can only get you to the outer ring as the waters rise. It's up to your diverse group of adventurers to get in, get safe, and survive. And as usual, payment on completion, but that a sign-up bonus of 2 uncommon magic items and 750gp were a nice donation. What awaits you inside the city hopefully is a cushy contract but they did hire adventurers, and you weren't the bottom of the barrel.
Players:
Lvl 5 Starting - Point buy Stats - All Classes/All Races Accepted, 2 uncommon magic items and 750g a person.
Style:
Battle Light, Diplomacy and creative problem solving heavy, (possibly puzzles)
Let me know if you'd be interested.