We recently completed flood risk identification work for the non-profit organization, First Street Foundation, which was made public and prompted needed conversations in the flood risk industry. I want to talk about that work and what it means for all of us because it is important and an opportunity to describe FEMA’s work in this context.
First Street has created a national flood risk model identifying more flood risk than you may be used to seeing if the FEMA flood maps have been your only source of flood risk in the past. First Street’s risk models are created by credentialed engineering and science professionals at multiple universities. And they incorporate climate change, which FEMA does not do. And it is a national-scale model, which you could call ‘big data’. And that model doesn’t necessarily incorporate every local flood mitigation measure like levees, dams, spillways, and the like. Therefore, First Street is going to show a lot more people at higher flood risk than they previously thought because First Street isn’t thinking about flood risk the same way FEMA thinks about it.
First Street isn’t wrong.
FEMA isn’t wrong either and I’ll get to that in a bit.
Our part was to analyze 142 million properties across the US and identify the FEMA flood zone. The FEMA flood zone can then be compared to First Street’s data so you can see the difference between FEMA’s view of flood risk and First Street’s view of flood risk. The purpose of our work was not to prove anybody wrong or right, it’s just a comparison between different views of flood risk. For example, FEMA has about 5 million insurance policies and about 2.6 million are in the high-risk areas. MassiveCert found about 8.7 million properties in FEMA’s high-risk areas. That doesn’t mean people are skirting the law or FEMA is doing a poor job. There are other factors in play.
Since MassiveCert is a flood zone determination company, we were able to apply our proprietary algorithms to calculate the most likely flood zone FEMA would assign to you. This is NOT a simple geospatial intersection – FEMA, the flood maps, the rules, and your property are much more complicated than that. This is the most comprehensive national analysis of FEMA’s flood zones ever completed to this degree of detail, so you have the best and most fair comparison possible.
So, we aren’t trying to say anybody has flood mapping wrong.
Then if First Street and FEMA show different results, how can they both be correct?
Because there is no such thing as “THE Floodplain”.
A flood is caused by a storm that produces more precipitation than rivers and lakes and shorelines can handle. So, the extra water flows outside of those rivers, lakes, and coasts across the land. That flow of extra water is a floodplain. Different storms produce different floodplains. The floodplain depends on how much precipitation you get. There isn’t a single floodplain, there are many many floodplains which are dependent on the storm and where it drops the precipitation, and how much precipitation it drops, and how fast the precipitation falls, and how fast that river or lake can move the excess water, and a whole lot of other factors.
FEMA draws A floodplain, not THE floodplain. Sometimes they draw several floodplains on their maps for the 100-year floodplain, the 500-year floodplain, the floodway, and others. But let’s just look at FEMA’s 100-year floodplain as their standard and what that really means.
FEMA’s “100-year floodplain” was created by Congress as a minimum standard to identify which properties must have flood insurance and which properties can optionally carry flood insurance if you’ve got a property with a loan backed by the feds. That standard is a line drawn on the map which indicates, based on past storms, where you have a 1% chance of flooding in any year. You could have a higher chance, but 1% is the minimum and a reasonable standard. If there is a 1% chance this year that your house falls down – it’s a good idea to get some insurance.
FEMA’s “100-year floodplain” is not designed to tell you the true flood risk level your property is facing. It is only a manufactured standard used as a cut-off line for a flood insurance Act to group you into two buckets: flood insurance is mandatory, or flood insurance is optional. It is not telling you the natural order of Mother Nature. You must make a line somewhere for our flood insurance laws, so 1% was reasonable and it’s just the Congressional standard floodplain, not THE floodplain. And there are federal standards about how to correctly create flood models to meet the standard. FEMA isn’t wrong and they actually do a very good job at maintaining standards and doing what they are charged to do. And MassiveCert has calculated the flood zone for 142 million properties according to that specific standard.
First Street has provided a flood risk model without the federal restrictions and without first trying to set a standard for who must have insurance and who doesn’t. First Street looks at risk from a different perspective so they can show the public the risk you may be facing when it is not colored by those federal restrictions.
The bottom line is that FEMA’s flood zone is not the definitive measure of your natural exposure to flood risk and total danger facing you. FEMA’s 100-year floodplain is just a federal insurance standard because a 1% chance of the house falling down this year is a reasonable place to draw a line.
The true and comprehensive flood danger for any property cannot be defined by your flood zone alone, and thus First Street Foundation, and similar organizations/companies, are showing you their view of flood risk based on the best science and engineering possible without federal restrictions.
So, they are both correct but meant for different purposes. It’s important to understand the distinctions and apply the different models appropriately. You can’t use the First Street model to comply with the Congressional flood Act and you shouldn’t dismiss the FEMA floodplain as inaccurate just because it differs.
If you have questions or comments or want to see how our data can help your organization’s flood risk analysis, please drop me a line.