Introducing the Space City Weather Flood Scale

Ever since Hurricane Harvey, a lot of people living in and around Houston become nervous at the mention of widespread, heavy rainfall. The mere suggestion of even minor flooding heightens tension. And after surviving Harvey, we certainly understand why.

In the months after Harvey, Matt and I got together to try and determine what, if anything, we could do to help ameliorate this situation. Eventually, Matt hit upon the idea of a “flood scale” that residents of the greater Houston area could use to calibrate their concerns about upcoming flood events. Over time, the scale evolved into a rating from Flood Stage 1 (street flooding) through Flood Stage 5 (Hurricane Harvey). Here’s what we came up with:

Space City Weather Flood Scale.

This scale is not officially sanctioned by any government organization. Nor are we seeking to usurp any authority from the National Weather Service—they command our highest respect in issuing flood watches and warnings. Rather, we felt there was a need for something like this, in advance of significant weather, to help our readers set expectations and manage their own anxieties. So we’re providing the scale as such a service. It remains a work in progress.

In truth, there are many, many ingredients that will determine the impact of a flood: the total amount of rain, intensity of hourly rainfall rates, how long the rains last, the preexisting saturation of soils, the time of year, and more. This scale attempts to incorporate all of those factors into the ranking the impact of a flooding event. It is not perfect, nor purely quantifiable, but is does represent our best attempt to determine what residents can expect.

So why are we introducing this scale now? Because we anticipate needing it for the coming Thursday through Saturday period. Absent a major change in the forecast models, we’ll begin to use the flood scale beginning in Tuesday morning’s post. For what its worth, our overall thinking hasn’t changed, we continue to see the potential for 3 to 10 inches of rain through Sunday morning for the Houston region.

45 thoughts on “Introducing the Space City Weather Flood Scale”

  3. Well…that makes me anxious. But since I was out and about during the May 2015 floods but none of the subsequent ones, forewarned is forearmed. Thanks, guys. Staying tuned.

  7. Matt/Eric – in industrial risk ranking this is what we call a “semi-qualitative” scale for assignment of event severity. There’s another axis which relates to the frequency of the event. Both values determine a relative level of risk that allows a company/individual to apply appropriate mitigation. In some of the Stages, you mention a number of homes affected. This would be more a quantitive measure if it was used for all Stages. Do you have other quantitive values that you use to assign a “Stage 1”, etc? Perhaps total rainfall in relation to previous events? Geographic area affected?

    • There are no hard, quantifiable barriers between the stages. It basically breaks down like this:

      Stage 1: Run of the mill street flooding, brief impacts to area roadways.
      Stage 2: More serious flash flooding affecting multiple roadways, longer delays. a few areas flooded.
      Stage 3: Home flooding (100s) and more widespread flash flooding on roads.
      Stage 4: Thousands of homes flooded.
      Stage 5: Bad, bad, bad

      The problem is you can’t really quantify all of these variables because they all matter. Tried to explain that here:

      “There are many, many ingredients that will determine the impact of a flood: the total amount of rain, intensity of hourly rainfall rates, how long the rains last, the preexisting saturation of soils, the time of year, and more.”

      Probably not a satisfactory answer, I know. But we’re not trying to earn a dissertation here, just trying to calibrate people’s expectations. Basically, we don’t want people looking at this weekend’s flood potential and thinking it’s another Allison when it’s probably a Stage 1 or Stage 2 type event.

      • Absolutely satisfactory. I was just curious if there were any variables rolled up into your stage assignments, that’s all.

  8. I have mixed emotions here. Thankful for you guys and your sage wisdom during times of wet crisis…Concerned that there is a need to “boil” such events to a scale of 1 – 5…Sobered to realize that we have experienced storms of intensity 3 to 5 in in 2015 – 2017.

  10. Bravo Zulu for being proactive in a non-hype way…frustrating this passed year hearing local and national TV weather folks hype ANY storm with a very non-specific phrase like “…this storm system has 23 million people in its path”…aarrgghhh!

  11. Stage 1: Don’t drive into flooded areas !
    Stage 2: Yes, it is simultaneously monsooning in Sugar Land and setting a new high temperature record in the Woodlands
    Stage 3: Stop driving into flooded areas !
    Stage 4: All five bayous and three rivers in Houston are out of their tertiary banks
    Stage 5: You should have left for the Rockies three days ago

    • I forgot to mention that I live 300 feet away from the Brazos River in Greatwood. We are forecasted to have two foot of river on our 12 foot tall levee by Thursday. We are in the process of raising our levees by two feet more from the levee raising of five feet seven years ago.

        • No joke. We avoided a levee test for 20,000 homes along the Brazos River in Fort Bend County when Harvey went south of Houston instead of north.

          There is a great explanation of the various floods along the Brazos river since 1899 in this blog. December 1913 was a doozy and one foot above our 1,000 year levee in Greatwood.
          http://lifeonthebrazosriver.com/Floods.htm

  13. Thanks guys.

    This can be a terrific tool; Potentially a game changer in the communication of weather events.

    Two minor questions. My home was flooded by the April 2009 event so I am sensitive, but I wonder if it is categorized correctly. Second, where is Ike in all of this? If you just consider water damage, Ike wasn’t that bad but if you consider wind damage and infrastructure damage, it was pretty bad.

    Thanks again, Great work.

  14. This is great for those of us with friends and family coming in for Rice commencement activities beginning on Friday. Trying to keep everyone weather aware coming from areas outside of Houston, but honestly a bit nervous about things being completely cancelled. Eagerly anticipating your Friday/Saturday forecasts!

  15. Oh Eric this is just wonderful! Thank you for such a fantastic way to measure the floods. This will certainly help me comfort my dear Fulgencio when the rains come. Blessings to all.

  16. I am flagging and keeping this in my inbox for future reference. Thank you for honest analysis without drama. God bless you all for your service to our community!

  18. My belief is that the ordinary guy that is not educated in your flood potential rating system will be totally confused by it. Using terms like flood potential comparable to X event are probably better than creating new jargon. Even comparing to a specific historical event will confuse folks that did not experience the event. Old time adjectives and adverbs are confusing enough for folks, I do not think a new rating system will simplify the complex issue. I’d avoid creating new jargon or rating systems that are not widely accepted throughout the weather forecasting community. I might change my stand if you change the scale to Should Katy Evacuate? Red/Amder/Green… 😉

  19. Y’all are awesome. You saw a need and stepped up. I will say, like others, reading this gave me a tiny anxiety attack. Realizing I was here for the two biggies (Allison and Harvey) is very sobering.

  21. You’re the hands down best source for weather facts around. From those (and Brazos river forecasts) I make my decisions but keep up the good work. Quantifying into absolute scale is not easy because to me a level 3 might be a level 5 if the river goes over it’s banks but so it is.

  22. Your information allows me to make logical decisions, not hype decisions.

  23. I think you two are the best regional meteorologists the Houston metro area has hands down. I appreciate the hype-less way you come across. Down to earth and completely rational and understandable. Thanks so much and God bless both of you.

  26. I’m against this. You guys are a great source of information, but this kind of generalizing and color-coding is the first step toward sensationalist reporting.

    Just the facts, remember? That’s why you have readership.

    • I appreciate that concern, but I think that their intent is the opposite. Right now mainstream news organizations are acting like the upcoming storm is a level 4 event, when Eric and Matt want us to know that it will only be a level 1 or 2. Plus they surely get tired of all the “I’ll be driving back from Dallas at 4pm on Thursday, should I be okay?” kinds of questions.

  28. Thank you very much for this flood scale. I really wish the Houston news would have something like this. I can use this scale to determine if I should go to Comicpalooza this weekend!

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