<p>I'm not sure whether anyone officially evaluates it (consistently), but here are a few ideas for checking it yourself (for the US, since you mentioned the NWS):</p>
<ul>
<li>On the precipitation end, you could compare the reported precipitation and duration to the <a href="https://hdsc.nws.noaa.gov/pfds/pfds_map_cont.html" rel="nofollow noreferrer">Precipitation Frequency Data Server (PFDS)</a>.  For example, during <a href="https://www.weather.gov/bou/Number1September2013Floods" rel="nofollow noreferrer">Colorado's 2013 floods</a>, a site in Boulder, CO recorded about 15&quot; of rainfall. That figure was for 7 days, but the description says most of it fell in 30 hours, so we'll say two days.  The PFDS, selecting that point (estimated:  40.0156° N,  -105.2800° E), says that 15&quot; is more than the 1000-year return interval precipitation for a 2-day (or, for that matter, a 7-day) storm.  A 1000-year, 2-day storm would be 9.4&quot;.  Therefore, we can say that, in that area, the actual rainfall exceeded a 1000-year storm.</li>
<li>For streamflow, <a href="https://streamstats.usgs.gov/ss/" rel="nofollow noreferrer">USGS StreamStats</a> can estimate peak flow statistics for a site if you go through the steps for the delineation and report tool, selecting &quot;peak flow statistics&quot;, and if you select a gage on the map you can view the &quot;StreamStats Gage Page&quot; with observed flow data (under the &quot;Gage Analysis Plots&quot; tab).  For example, USGS gage 06730200 (on Boulder Creek) had a peak discharge of 8400 cfs during the September 2013 flood.  For estimated floods, StreamStats only goes up to 0.2% (500-year), but that figure is 7420 cfs (generating a report for peak flow statistics).  Thus, the flood was more than a 500-year flood.  Those are estimated values only, but it provides some reference point.</li>
</ul>

CC BY-SA 4.0
2024-04-18T16:53:45.033Z
I think streamflow data is probably the only way you can make a direct estimate.  Here's another streamflow gauge data link:  https://water.weather.gov/ahps/index.php
f.thorpe
CC BY-SA 4.0
2024-04-16T22:42:56.260Z
2024-04-16T22:42:56.260Z
damp_civil
<p>The 100-year flood line runs through my property (Midwest - United States). I am always curious when I see flooding how close to a 100-year flood it might be. Is there any way to know? Does any official service/site post data that rates how significant a flood was? The National Weather Service issues flood warnings. After a significant rainfall, is there a way to know how the flood was rated?</p>

CC BY-SA 4.0
2024-04-16T04:47:55.183Z
flooding is hydrology not meteorology.
trond hansen
CC BY-SA 4.0
2024-04-16T08:15:17.113Z
I assume because you mention the National Weather Service that you're interested in the US specifically, or are you interested in other countries?
Deditos
CC BY-SA 4.0
2024-04-18T06:43:03.600Z
I am interested in the US only.
JWess
<hydrology><flooding><severe-weather>
Does a weather authority rate/measure floods after they happen?
JWess
# Does a weather authority rate/measure floods after they happen?

(Asked by: username_0 on 2024-04-15)

The 100-year flood line runs through my property (Midwest - United States). I am always curious when I see flooding how close to a 100-year flood it might be. Is there any way to know? Does any official service/site post data that rates how significant a flood was? The National Weather Service issues flood warnings. After a significant rainfall, is there a way to know how the flood was rated?

**Tags:** hydrology, flooding, severe-weather

> **Comments:**
> **username_1**: flooding is hydrology not meteorology.  
> **username_2**: I assume because you mention the National Weather Service that you're interested in the US specifically, or are you interested in other countries?  
> **username_0**: I am interested in the US only.  

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## 1 answers

### Answer by username_3 on 2024-04-16. Score: 4

I'm not sure whether anyone officially evaluates it (consistently), but here are a few ideas for checking it yourself (for the US, since you mentioned the NWS):

* On the precipitation end, you could compare the reported precipitation and duration to the [Precipitation Frequency Data Server (PFDS)](https://hdsc.nws.noaa.gov/pfds/pfds_map_cont.html). For example, during [Colorado's 2013 floods](https://www.weather.gov/bou/Number1September2013Floods), a site in Boulder, CO recorded about 15" of rainfall. That figure was for 7 days, but the description says most of it fell in 30 hours, so we'll say two days. The PFDS, selecting that point (estimated: 40.0156° N, -105.2800° E), says that 15" is more than the 1000-year return interval precipitation for a 2-day (or, for that matter, a 7-day) storm. A 1000-year, 2-day storm would be 9.4". Therefore, we can say that, in that area, the actual rainfall exceeded a 1000-year storm.
* For streamflow, [USGS StreamStats](https://streamstats.usgs.gov/ss/) can estimate peak flow statistics for a site if you go through the steps for the delineation and report tool, selecting "peak flow statistics", and if you select a gage on the map you can view the "StreamStats Gage Page" with observed flow data (under the "Gage Analysis Plots" tab). For example, USGS gage 06730200 (on Boulder Creek) had a peak discharge of 8400 cfs during the September 2013 flood. For estimated floods, StreamStats only goes up to 0.2% (500-year), but that figure is 7420 cfs (generating a report for peak flow statistics). Thus, the flood was more than a 500-year flood. Those are estimated values only, but it provides some reference point.

> **Comments:**
> **username_4**: I think streamflow data is probably the only way you can make a direct estimate.  Here's another streamflow gauge data link:  https://water.weather.gov/ahps/index.php  

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