PRE-ANALYSIS (per-gauge facts for 2026-05-20):
| Gauge | First | Max | Last | Intraday Low | Low→Peak Rise |
|---|---|---|---|---|---|
| Boxley | 2.46 ft @ 00:00 | 2.54 ft @ 01:30–02:30 | 2.26 ft @ 23:30 | 2.26 ft @ 23:00 | n/a (monotonic fall after early peak; +0.08 ft rise from 00:00 in first 90 min) |
| Ponca | 230 cfs @ 00:00 | 230 cfs @ 00:00 | 143 cfs @ 23:30 | 143 cfs @ 23:30 | n/a (pure recession) |
| Pruitt | 4.41 ft / 293 cfs @ 00:00 | 4.60 ft @ 08:45–09:45 / 354 cfs @ 08:45 | 4.34 ft / 272 cfs @ 23:30 | 4.34 ft @ 23:30 | +0.19 ft / +61 cfs from 00:00 to 08:45 (~9 hr) |
| St. Joe | 3.65 ft / 248 cfs @ 00:00 | 5.20 ft / 937 cfs @ 20:45 | 5.20 ft / 937 cfs @ 22:45 | 3.65 ft @ 00:00 | +1.55 ft / +689 cfs from 00:00 → 20:45 (~21 hr) |
| Harriet | 4.31 ft / 594 cfs @ 00:00 | 4.61 ft / 808 cfs @ 22:45 | 4.61 ft / 808 cfs @ 22:45 | 4.05 ft / 431 cfs @ 13:00–14:30 | +0.56 ft / +377 cfs from 13:00 low → 22:45 (~10 hr) |
| Richland | 2.15 ft @ 00:00 | 2.15 ft @ 00:00 | 1.86 ft @ 23:00 | 1.86 ft @ 23:00 | n/a (pure recession from prior-day peak) |
| Bear Cr | 2.08 ft / 13.2 cfs @ 00:00 | 2.14 ft / 16.0 cfs @ 22:45–23:15 | 2.14 ft / 16.0 cfs @ 23:15 | 2.08 ft @ 00:00 | +0.06 ft / +2.8 cfs from 00:00 → 22:45 (~23 hr slow rise) |
Essentially dry day. Basin-max 24-hr QPE: 0.014" (Boxley zone — a few isolated cells along the headwaters). All other zones registered ≤0.011". This is the trailing edge of the Day 80 major event; the convective complex has cleared. Today is a recession + propagation day for the Day 80 forcing.
This day is dominated by mainstem flood-wave propagation from Event 11 (Day 80) rather than today's QPE.
Today's QPE is too small to drive responses (per auto-context). All today's rises are attributable to Day 80 (Event 11) forcing. Computing transfer ratios for the now-resolved Event 11 peaks:
St. Joe (Event 11): - Pre-event 3.48 ft / 198 cfs (Day 80 00:00). EOD-rising peak ≥5.20 ft / 937 cfs @ 20:45. Rise ≥ 1.72 ft / +739 cfs. - Zone QPE 1.60", peak 1-hr ~14–17 UTC on Day 80. - Lag: Day 80 peak 1-hr ~10–12 CDT → St. Joe peak Day 81 20:45 = ~33–35 hr lag (consistent with St. Joe integrating 14 HUC12s + upstream propagation). - Transfer ratio: 1.07 ft/in or ~462 cfs/in. - Antecedent: DRY (7d ~0.25"). - Comparison to prior: Event 8 (wet antecedent) St. Joe transfer ratio was ~0.8–1.0 ft/in; Event 10 (moist) similar. Today's 1.07 ft/in is higher than expected for dry antecedent — but the watershed is 38.7% of the basin and the storm forcing was uniform across all upstream zones too, so cumulative routing dominated over local infiltration loss. Within 30% of prior; no flag.
Harriet (Event 11, still rising at EOD): - Pre-event 3.67 ft / 232 cfs (Day 80 00:00). EOD ≥4.61 ft / 808 cfs @ 22:45 still rising. Rise so far ≥ 0.94 ft / +576 cfs. - Harriet zone QPE 1.76", but Harriet integrates upstream too. - Lag (Day 80 zone peak ~10–12 CDT → 22:45 Day 81 = ~35 hr) — appropriate for the lowest mainstem gauge. - Transfer ratio (zone-only basis): ~0.53 ft/in so far, but peak not yet reached. Will refine tomorrow. - Antecedent dry (7d 0.22").
Pruitt (Event 11 sub-peak today): - Pre-event 3.43 ft (Day 80 early). Today's secondary peak 4.60 ft @ 08:45. Rise from absolute Day 80 pre-event ~1.17 ft. - Zone QPE 1.93", peak 1-hr 16:02 UTC Day 80 = 11:02 CDT. - The Pruitt response had two peaks: 3.92 ft @ 15:00 Day 80 (4-hr lag, first wave) and 4.60 ft @ 08:45 Day 81 (~22-hr lag, second wave from late Day 80 forcing at 22:00 CDT — Day 80 had a 22:00 hourly rise of 0.23 ft, the largest Pruitt hourly rise). - Transfer ratio (cumulative): 1.17 ft / 1.93" = 0.61 ft/in. Dry antecedent (7d 0.07"). - Comparison: Prior Pruitt dry-antecedent observations are sparse; Event 9 produced ~0.5–0.7 ft/in range. Consistent, no flag.
Richland Creek (Event 11, now resolved): - Pre-event 1.18 ft (Day 80). Peak 2.20 ft @ 21:30 Day 79 (Day 80 in study chronology — peak occurred on Day 80 evening). Rise 1.02 ft. - Zone QPE 1.39", peak 1-hr 17:02 UTC Day 80 = 12:02 CDT. Peak lag ~9.5 hr. - Transfer ratio: 0.73 ft/in. Dry antecedent (7d 0.30"). - Comparison to prior Richland: Event 9 dry-antecedent yielded a higher ratio (~0.9–1.1 ft/in for similar QPE). Today's 0.73 ft/in is on the lower end — could reflect that the storm delivered rain over wider area without concentrating in Headwaters Richland (HUC12 0306) where the steep flashy response occurs. Within ~30% range, no flag, but interesting spatial signal.
For the first time in the study, we have a clean propagation cascade visible on a single recession day. Mainstem-only peak times for Event 11:
| Gauge | Peak time | Peak value | Δt from Boxley |
|---|---|---|---|
| Boxley | 05-20 01:30 | 2.54 ft | — |
| Ponca | 05-19 21:45 | 234 cfs | (peaked before Boxley; locally-driven by Ponca-zone QPE) |
| Pruitt | 05-20 08:45 | 4.60 ft | +7.25 hr |
| St. Joe | 05-20 20:45 | 5.20 ft (still rising) | +19.25 hr |
| Harriet | 05-20 ≥22:45 still rising | ≥4.61 ft | ≥21.25 hr |
Note Ponca peaked before Boxley because both received direct simultaneous forcing on Day 80; Ponca's smaller, flashier zone responded first. This is consistent with Event 11's "simultaneous direct forcing at every gauge" character.
Boxley → Pruitt propagation: ~7.25 hr. With Pruitt's drainage area (513 km²) vs Boxley (92 km²), most of this lag reflects flow time + Pruitt-zone integration rather than pure routing. Consistent with prior estimates of ~4–8 hr Boxley→Pruitt under wet conditions.
Pruitt → St. Joe: ~12 hr (~8:45 → 20:45). St. Joe's much larger drainage (1342 km² zone, 1932 km² cumulative) and additional Richland inflow extends the integrated wave.
Event 11 (Day 80–81+) totals through EOD Day 81:
| Gauge | Pre | Peak observed | Rise | Status |
|---|---|---|---|---|
| Boxley | 1.82 ft | 2.54 ft | +0.72 ft | RESOLVED (falling) |
| Ponca | 70.8 cfs | 234 cfs | +163 cfs (3.3×) | RESOLVED (falling, back near 143 cfs) |
| Pruitt | 3.43 ft / 56.6 cfs | 4.60 ft / 354 cfs | +1.17 ft / +297 cfs | RESOLVED (falling) |
| St. Joe | 3.48 ft / 198 cfs | 5.20 ft / 937 cfs | +1.72 ft / +739 cfs | STILL RISING at EOD |
| Harriet | 3.67 ft / 232 cfs | 4.61 ft / 808 cfs | +0.94 ft / +576 cfs | STILL RISING at EOD |
| Richland | 1.18 ft | 2.20 ft | +1.02 ft | RESOLVED |
| Bear Cr | 2.06 ft | 2.14 ft | +0.08 ft | slow rise continues |
Event 11 has now demonstrated: a major dry-antecedent watershed-wide event produces (a) flashy headwater response (Boxley/Ponca/Pruitt resolve within 24–36 hr), (b) sustained integrated downstream wave at St. Joe and Harriet still building 36+ hr post peak-QPE, and (c) Bear Creek remains a low-responsiveness zone even with 1.11" zone QPE — its DRY antecedent (0.24") + zone characteristics limit response to ~0.08 ft total.