What this tool does
Separate known wet groups with observed dry intervals, not merely elapsed time between two rain readings. Keep incomplete fragments visible.
When to use it
After retaining original observations and confirming the record basis. Run this decision independently; the other rainfall tools answer different questions and are not required merely to obtain a number.
Calculation or decision method
Every positive depth is wet. Separate wet groups when the intervening duration of known zero-depth intervals is greater than or equal to your chosen dry gap. Do not infer a dry interval from a missing reading.
Missing values or skipped steps split the observed record into fragments with unknown boundaries. Sufficient later observed dry time can reestablish a bounded edge. Record start/end does not automatically establish a complete storm.
Start = first wet interval end − interval length. Duration ends at the last wet interval end; it includes short internal dry gaps but not bounding dry runs. Mean intensity = observed depth / that duration. Peak interval intensity = largest entered interval depth / interval hours. It is not an instantaneous peak or rolling maximum.
Worked example
Hourly depths 0,0,2,1,0,0,4,0,0 and a 120-minute dry gap give two bounded events:3 mm over 120 minutes and 4 mm over 60 minutes. Peak interval intensities are2 and 4 mm/h. Increasing the chosen gap to 180 minutes joins the wet groups, with insufficient leading/trailing dry context to call both edges bounded.
Assumptions
All inputs are interval depths with end timestamps, one fixed-offset clock, one accumulation length and one selected unit. Any positive trace remains wet. If changing the chosen gap changes event counts, that is a scenario result—not evidence that one gap is universally correct.
Input and precision rules
Plain decimal, nonnegative depths; blank or NA means missing. Supported nonzero numbers run from 1e-12 to 1e9 in the entered basis. Inputs use ordinary browser floating-point precision, not arbitrary-precision metrology. Reconcile unsupported missing codes, tip counts, timezones, intensity values and changing clocks before entry. A malformed row stops the run rather than disappearing.
Limitations
Unknown-boundary fragments are not complete independent storms. This tool does not infer trace thresholds, repair gaps, fit event frequencies, derive return periods/IDF, reconstruct winter precipitation or forecast flooding. A dry event count of 0 differs from an all-missing record with no observed rainfall total.
Keep the review packet
Retain the dry-gap setting, interval basis, censor flags and original series together. Resolve field gaps before applying methods that require complete events. Exported event summaries are audit output, not a replacement interval series. The screen/print preview is limited to 100 rows; audit CSV downloads retain every computed row. Copy result includes the full entered CSV and configuration. Keep sensitive project data within your own handling procedures; the site does not upload it.
Sources
- IETD method documentation — interval rainfall and chosen dry gaps
- Environmental Science: Advances — Extensive rainfall data analysis (2023)