DP, but it seems the annual rain amounts in this area has not increased. NWS has all this data and there aren't any obvious trends. Meanwhile, I looked at the first street maps for North Potomac, Potomac/Rockville area and there are indeed a good number of houses in the flood zones. Is the solution that all these people should sell their houses because a random company predicts flooding based on...what exactly, some proprietary model?

FEMA maps are notoriously out of date, OP. Do NOT put any faith in them.

I believe you are at higher risk of flooding based on the proximity of the storm drain. It's hard for you to accept this, but with the higher frequency of more extreme weather events, that storm drain is a risk to your property. You may be on slightly higher ground, but when (not if) the water rises 30 feet in 3 hours, you won't be scoffing anymore.

Before FEMA updates its map for your area, you might want to sell. That's what people check, usually, and a flood-prone property is unsaleable.

I took a look at First Street. Our house and the one we rented when we moved here, 2 doors west, are 1/10. Always dry basements.
The ones a few doors farther west are 7/10. Believable. One has a sump pump that ran constantly until it sold and new owners did french drains.
When we moved here 40 years ago I got USGS soil maps for fun. There is a change in the soil type right at that boundary. Also allegedly an underground stream per a very old man who had lived next door all his life when we met him then.
There are culverts at the running trail past there and a little stream, maybe emergence of the underground one in the woods there, feeding into 4 mi run. That is slightly downhill of us.

Anonymous wrote:You have an active storm drain running under your property? What if it clogs or breaks and starts dispersing that water underground?

The house sits significantly higher and a good distance away from the storm drain. There is a lot of water coming out of the drain during the huge storms we have had and it almost forms a little river straight to the steam, but this is all away from the house. Our property is over 4 acres so while this may sound scary, the water is really not close to the house.

The first street maps actually show a lot of houses in MoCo subject to flooding. I feel like people are not aware this exists and will be surprised when they try to sell their house.

My issue with this company is that they do not really share their methodology, it is trying to predict the future, and yet it is negatively affecting home prices today based on this opaque methodology. There is also the obvious conflict of interest because they are longer a non profit and make money selling you flood insurance. And researching on reddit, people do not get anywhere trying to appeal their "Flood Factor" ratings.

How is this not a class action lawsuit waiting to happen?

You have an active storm drain running under your property? What if it clogs or breaks and starts dispersing that water underground?

This explains why Zillow started using First Street: https://investors.zillowgroup.com/investors/news-and-events/news/news-details/2024/Zillow-introduces-First-Streets-comprehensive-climate-risk-data-on-for-sale-listings-across-the-US/default.aspx

And, an article on FEMA v. First Street: https://www.preventionweb.net/news/fema-maps-said-they-werent-flood-zone-then-came-rain

Anonymous wrote:

Anonymous wrote:Look at federal flood maps, they’ll explain everything.

It’s probably based on probability and your neighbors may be on one side of a line that says 51 out of 100 times their house is okay and your is on the side that says 51 out of 100 it’s not - basically the same risk but you’re on the wrong side of the line.

Either way, there’s no way you can tell if something is right or wrong without looking at federal flood maps. It’s not a thing you can feel.

The FEMA flood maps don't show flooding anywhere near my house.

Federal maps show probability. Find the probability.

I just looked. My neighborhood neighborhood is zone X but also has some areas show up on the Redfin flood map, which seem to.be neighborhood water retention pond type areas. At least in our neighborhood, the homes nearby those areas on the Redfin map DO have trouble with water control along with some foundation issues. It's probably best to consider the data together.

You may be able to appeal the rating - more info here:
https://help.firststreet.org/hc/en-us/articles/360048001274-Changing-your-home-s-details-on-First-Street

Just note - hour house not being in a FEMA floodplain isn't necessarily meaningful. Plenty of areas in the US are having massive floods now outside of FEMA floodplains, especially in areas where the maps haven't been updated in decades. Higher temperatures have increased extreme precipitation events and the First Street Foundation maps include recent flood extent data. Also, additional development and increase in impervious area also contribute to higher stormwater runoff even if precipitation stayed the same (although it hasn't).

The rating is for the entire property (and over the long term so it may be a risk estimated over the next 30 years). Older builders were not idiots and typically built on the highest elevation part of any parcel. So your house may be fine while an edge of the property may get water and it will still have a flood warning. If that is the case you can just explain when selling. You can get a land survey and argue with the rater for an adjustment but I don't know how effective that is.

Anonymous wrote:Look at federal flood maps, they’ll explain everything.

It’s probably based on probability and your neighbors may be on one side of a line that says 51 out of 100 times their house is okay and your is on the side that says 51 out of 100 it’s not - basically the same risk but you’re on the wrong side of the line.

Either way, there’s no way you can tell if something is right or wrong without looking at federal flood maps. It’s not a thing you can feel.

The FEMA flood maps don't show flooding anywhere near my house.

Look at federal flood maps, they’ll explain everything.

It’s probably based on probability and your neighbors may be on one side of a line that says 51 out of 100 times their house is okay and your is on the side that says 51 out of 100 it’s not - basically the same risk but you’re on the wrong side of the line.

Either way, there’s no way you can tell if something is right or wrong without looking at federal flood maps. It’s not a thing you can feel.

And by creek I mean basically a stream, barely any water there normally but has high banks and then it is gentle uphill to the house.

I just discovered that my house is rated 7/10 on the First Street flood factor that shows up on redfin. We bought the house about 3 years ago and I definitely do not remember it being rated that way then.

I have no idea what they base this stuff on but it seems inaccurate. My neighbors are all rated 1. We have had massive rain this year and we have never had water running or pooling near the house. Our old house which was at the bottom of a neighborhood hill had way more water issues and it is rated a 1/10. The only thing I can think of is that we have a storm drain easement on our property so there is a lot of water running out of that drain into the creek behind us but this drain is like 100 feet downwards from our house draining away. We are maybe 600 feet away from the creek, so not that close.

Question is, is there anything I can do? It seems so sketchy that this company gets to "predict" flooding and then ruin home values. Are we just screwed with our home value?