Section outline

  • The hazard that kills more people in an average year than tornadoes, and the one a spotter is least trained to describe. Seven lessons on what the words mean, what makes the rain sit still, why the same rainfall floods five regions five different ways, and what you can actually measure from a roadside.

    • What the words mean Page
      Students must
      View

      Flash flood, flood, coastal flood, debris flow. Four separate events with four separate definitions, quoted rather than summarized. (25 min)

    • Why the rain stops moving Page
      Students must
      View

      Rate times duration. The ingredients that set the rate, the configurations that stretch the duration, and why the storm that floods you is often the quiet one. (30 min)

    • Flooding is local Page
      Students must
      View

      The same rainfall floods five places five different ways. Which one you live in decides what to watch, what to expect, and which rules of thumb will mislead you. (25 min)

    • Why floods kill Page
      Students must
      View

      The numbers, where they come from, why they disagree with each other, and the three sentences of NWS wording worth memorising exactly. (25 min)

    • What you can actually observe Page
      Students must
      View

      Depth against a curb and a tire, flowing against ponded, a rain gauge read to hundredths, and the difference between a flooded street and a flash flood. (30 min)

    • What the radar thinks it saw Page
      Students must
      View

      QPE, flash flood guidance, recurrence intervals and FLASH. What they measure, what they do not, and why the heaviest rainfall is the kind the radar estimates worst. Which is biased low by design. (30 min)

    • Two floods, and how this platform checks yours Page
      Students must
      View

      Two documented events with public data, then the reason a flood report gets a wider window and a longer memory than every other report here. (20 min)