what does this mean exactly? the city is way more likely to be flooded by ocean swells from the lake, as in what happened shortly after hurricane Katrina.
NO has minor street floods quite often from rain because it all has to be pumped out of the low lying city.
the big thing is the land erodes very quickly and water must constantly be re-directed. This happens all over the state. since the ground is not very stable and is always changing this is a big challenge. everything around the city on all sides is very wet swamp except to the north which is the lake.
Sure this is going to be the case in any sandy, marshy area. Plum Island and the Joppa Flats on the Merrimack River are the same. The Flats have changed their shape, according to my Geology professor, about 55 times since 1861, and Plum Island its self is disappearing into the Atlantic more and more with every increasing storm. Plum Island, just like many of the coastal islands along the Atlantic and parts of the Gulf region, are barrier islands. They naturally protect the mainland from the bigger storms as they take up the brunt of the waves, and naturally grow and shrink as the weather and waves change. The problem is we like to fix things... In other words, the Army Corp of Engineers and other hair brained construction "gurus" disturbed the natural flow of water. Let's face NO and the rest of the state and Gulf Coast is pretty much a big marsh. Water has a natural direction it wants to flow in. If you build up and channel around it, it will flood over its banks. This is why the water off the lake flooded the city during Katrina. The water had nowhere else to go because it's natural dispersion areas was blocked. This is why there are so many floods up and down the Mississippi River during the spring. The natural flood plains have been built up or leveed off and made into farmland. So now a river which will swell over its banks during higher water has nowhere else to go except up and over the walls.
And yes, I say this from experience as well. About 35 years ago, my old town of Andover. Yes, the famous snooty town of Andover, decided to "fix" a small swamp located behind my house because there were plans to put in 25 houses in the 12 acres of land out there that never materialized. The engineers came in and channeled the little creek that flowed mostly in the spring into a small drain in the ground. Come the next spring, we now have water flowing into our basement. The water was actually seeping up from the ground and filling up my basement and did so until we were able to get a pump put in. My house wasn't one of those new jobs, it was an 1872-76 farmhouse that never got wet. It got damp normally, but never had flowing water in it. It cost the town over $20,000 to repair the damage caused to the property. We've since moved away over 15 years ago now, but had some good history on the property because a neighbor was related to the original owner, and we found out all kinds of interesting things about the property like the now missing barn and pile of old coke from the coal furnace...
Now you think they'd learn...
A few years later, another developer wanted to put houses in the same spot and the town went along with it immediately. The neighborhood appealed because of the noise, traffic from the additional street, and flooding. This time though the builder used a comprehensive permit meaning they can squeeze as much as they want on the land anywhere without appeals from abutters because this was for so-called low income. At the time houses were going for $300K in the town, and they considered $100K as low income property. All they need to do is put in one $100K house and they can get away with the comprehensive permit clause. Typical developers...
With this clause in hand, they set out to start construction and had to do some surveying and put markers on the property, even put in markers where they wanted to put in a holding pond for another wetland located in the area - a feeder to the one they put underground before. The residents were in an uproar because the town let them and appealed to the town government to no avail. A survey was done by my dad and other people that formed a committee. My dad did some maps up using Photostats and blowups of my topographic maps I had. He had all the equipment and ability to do this because he's a graphic artist... His presentation used the data gathered from the neighbors, which encompassed two full blocks out into the surrounding area in addition to my street. Whatever property was wet, or had water problems since the town played with the wetlands, was colored in red, others were white. When all was done, there was quite a shocking display of whose basements were in troubled waters!
The case got stuck in appeal with the conservation commission who worked mostly for the developers on 99.9% of the cases. They kept pushing things off to "the committee" for further review and stalled hoping everyone would go away. Finally, it took a court order and the state environmental commission to review the appeal because of the comprehensive permit. It looked pretty bad until one of the state officials asked to see the map and survey the land himself. It as late April or early May and there had been some rain - a bit more than normal. The peeper frogs were chirping away, and everything was wet, really wet. The committee, the state officials, the conservation commission head, and the rest of the meeting crowd went for a walk into the woods. Where that survey team put their markers outlining their holding pond location, there were frogs swimming in pools. Other places which had marked a fixed channel was flooded way over its banks and even had formed a vernal pond outside of the area. The developer blamed the residents for touching his markers, but the state didn't buy into that and declined the project. This, by the way, is only one of many few that are actually declined.
In the end the developer got to build only four small houses on each end of the property, and one of them had to be "low-income". When putting the road at my end called Gudrun, it took about 15 truckloads of fill to build up enough of a fill to keep the ground from sinking, and even to this day the ground keeps sinking in that place. As the dump trucks were delivering dirt, the neighborhood got to calling the road Mud Run as they had what looked like sloppy clay instead of a raised land for a roadway. One of these properties today is constantly flooded and a previous homeowner sued the builder.
I found out later from a local geologist, that the reason my basement was flooded, even though the house is up hill and about 3/4 acre or more from the creek area, is there is a thin layer of sand and silt sitting on a hard layer of granite. Think of a cake on a plate. What the town had done is push the water outwards by trying to channel it, causing what is called lateral flooding. Instead of the water flowing on the surface, it traveled along the under surface on the granite ledge and into other lower places like my basement. I forgot to mention too that my backyard, in particular the lower area, had become a wet marsh caused by the displaced water, and during a subsequent heavy rain and windstorm a few very old oak and ash trees fell over because the ground was compromised underneath them by the raised water table.
There as another incident, which I won't bother to discuss here that was a bit more interesting. If you want to hear about that one, I'll gladly PM you. It's quite amusing and involves a developer racing ahead of a flood of water as his holding pond broke...
John