Questions re building on AE flood zone land (New Bern, Washington: insurance, mortgage)

[goldenage1]

Originally Posted by assez

How bad is the flooding in the Oak Island/St James area? Is it very different on the ICW than in the marshy areas?

I don't really understand the question. If you get a hurricane, you will get the same amount of rain, whether you are on the ICW or on a marsh. The slope of the lot will determine how close the water gets to a house. So, the effect is not much different.

BTW, St James is at a slightly higher elevation than Oak Island. You should just get a detailed elevation map of any lot you think of buying, and evaluate how much risk you are willing to take.

BTW, when I was on Oak Island last summer, there was standing water in many places on the roads after a few days of rain. There is very little slope on Oak Island. My unscientific opinion is that if it ever gets hit by a hurricane like Fran or Katrina, many parts of Oak Island would be under several feet of water. The northern parts of St James would fare better, because the elevation is higher.

[assez]

We have never lived in a flood plain and I am not sure how to assess the risk - or even what questions to ask which is why I turned to this forum. I understand about building up - my question is if there is a weather event (hurricane?) what happens to the houses in the flood plain. If they are built high and cautiously is there damage? To what extent?
I know that this is vague and I appreciate any & all feedback.

[assez]

In other words... How does one evaluate the risk?

[ditchoc]

Originally Posted by assez

How bad is the flooding in the Oak Island/St James area? Is it very different on the ICW than in the marshy areas?

Lets think about this a second.

SJP is very near the ocean. Water is salty and there are tides. Tides change on average about 2-3 feet, some time a bit more depending on the wind, moon etc.

The ICW water level goes up and down with the tides. The major marsh land in SJP is called Polly Gully. The water in Polly Gully goes in and out with the tides. That should be pretty obvious that the water level in Polly Gully, the ICW and the ocean are all pretty much the same, e.g. sea level.

Along the water way and along the marsh land the Federal government says the 100 year flood plane is about 10-11 feet. That means that once every 100 years (or a 1% chance on any given year) the water level in the ocean, the ICW and around the marsh land will probably rise 10-11 feet above average. Again, if the moon and wind have their way it might possibly be a bit more.

So now the bottom line is, how high is your house above sea level.

The first part of that is, how high is the land you intend to build the house on. Most land in the area, except that right on the water, is at about 10-11 feet or about the same as the 100 year flood level. Property right on the water or marsh land may only be 3-4 feet above sea level.

Now you will see most houses on the water are built on pilings. It may not be immediately obvious at first because the owners like for their homes to look nice in SJP so they enclose the lower level of pilings so the lower level looks like the upper levels. On closer examination you will see the lower level, though enclosed, is actually just storage and garage. In many cases, on the inside you will not see any drywall or finishing or hot water heaters etc at ground level. The outside is just a facade to look nice. Then you will notice steps going up to a front porch and front door at the second floor level. This is where the real living space begins, on top of the pilings some 8 to 10 feet above the ground. So now the first floor is 3-4 feet (the ground level above sea level) plus another 8 to 10 up on pilings or possibly as much as 14 feet above sea level. If a 10-11 foot 100 year flood happens, the main house is safe and all that floods is the storage/garage space.

The same logic applies to homes a bit further away from the water front that may be on land that is 10-11 feet above sea level except to get above the 100 year flood plane they only need to raise their house 3-4 feet to be safe. Most foundations do this anyway.

Even further away from the water, in SJP up closer to 211, the land elevation is probably closer to 15 or 20 feet above sea level. Not much to worry about there.

Keep in mind that a lot of SJP is in a low lying area. There are many ponds and small lakes every where that make for nice scenery and more importantly, they provide a place for water to go. Heavy rains still cause standing water in the streets and swale's along the road edge. Usually the water runs off and drys up pretty quickly. No doubt there are a few problem areas but the POA seems to be pretty pro active in fixing these.

Finally SJP is about a mile as the crow flies from the ocean. There are hurricanes from time to time and mother nature in not a force to be reckoned with. In 1954 Hurricane Hazel hit Oak Island and only five buildings were left standing. No amount of planning, pilings, storm drains or ponds are going to matter much with a 18 foot storm surge that was recorded in Calabash. Hazel killed over 1,000 people. That is pretty sobering. We like to think we are smarter, better building codes, better weather forecasting and so on. A category 1 or 2 hurricane is generally not much to worry about. A category 3 is iffy, most people will just batten down and ride it out. I guarantee that should a category 4 or greater head toward SJP, I will be far away inland.

[goldenage1]

Originally Posted by assez

I understand about building up - my question is if there is a weather event (hurricane?) what happens to the houses in the flood plain. If they are built high and cautiously is there damage? To what extent?

Let's say a house is on pilings. Assume that what is stored on the ground level is flooded with four feet of water. A car would be ruined. Washing machines, dryers and water heaters will be ruined. If the HVAC is not elevated, it will be ruined and have to be replaced. The pilings and insulation could become moldy. Insulation and drywall will probably have to be replaced. If debris had floated and run into the pilings, the pilings may be structurally damaged and have to be replaced. A storm surge could also push the house off the pilings.

So even if the contents upstairs may be safe, the damage could still be between several thousand and tens of thousands of dollars.

Other damage caused by hurricanes is from flying debris, like pieces of roofing and tree limbs. Flying debris can pierce windows and siding, and expose the rest of the house to damage from rain entering.

[assez]

Wow.how often does this type of scenario happen?

[carolinadawg2]

Originally Posted by assez

Wow.how often does this type of scenario happen?

What scenario? A "100 Year Flood"? There is a 1% chance of it happening in any given year, so the short answer is, not often.

[rjsurfer]

I'm on the Intracoastal on Oak Island and also sort of overlook St James (to the East).

There are many lots along my street that are naturally high due to the contours of the land and with being on pillings my first floor is 31 feet above sea level. According to my UNTRAINED eye most of St.James appears to be sitting a bit lower especially by the Intracoastal.

I'm sure many residents of St. James will chime in with more accurate elevation readingsD

Ron W.

[assez]

I'd love to hear what happens in a "norma" year water elevation wise. With a first floor 31 feet above sea level my guess is that you are not impacted - correct? What about folks who are lower?

[goldenage1]

Originally Posted by assez

I'd love to hear what happens in a "norma" year water elevation wise. With a first floor 31 feet above sea level my guess is that you are not impacted - correct? What about folks who are lower?

Yes, if you are 31 feet above sea level, you probably won't be impacted by sea-side flooding. But, you should not look at a "normal" year, because flooding is unpredictable. You should build to mitigate the worst case scenario.

Frankly, I don't think you should buy a lot in a flood zone if you don't understand the risk of a hundred year flood. It is a 1% chance that the big one could happen at any time. If you live in the house for 30 years, you have been exposed to the risk 30 times.

The other risk is hurricane frequency. Hazel happened 61 years ago. Fran happened in 1996, and wiped out much of Topsail Island. Others have caused less damage, but some folks say we are overdue for a big one.

Another issue is coastal subsidence. The sea level is rising along parts of the coast. You should be researching the geology of St James if you are still interested in the flood zone lot.