Daily Analysis

Day 61 — 2026-04-30 — Event 8 recession day, peaks captured at St. Joe and Harriet

1. PRECIPITATION SUMMARY: Essentially zero. Trace amounts (<0.005") in scattered HUC12s. No new forcing. This is a clean recession day.

2. GAUGE RESPONSES — Event 8 peaks now confirmed:

Gauge	Day 60 status	Day 61 peak	Time of peak	Recession by 22:45
Boxley	3.24 ft falling	(peaked Day 60 @ 4.10)	—	2.95 ft (-0.29 ft over 24 hr)
Ponca	463 cfs falling	(peaked Day 60 @ 747)	—	368 cfs (-95 cfs / 24 hr)
Pruitt	651 cfs / 5.41 ft falling	(peaked Day 60 @ 893 / 5.98)	—	449 cfs / 4.87 ft
St. Joe	2150 cfs / 6.84 ft rising	2260 cfs / 6.96 ft	00:30 CDT	1530 cfs / 6.09 ft
Harriet	2120 cfs / 6.02 ft rising	2430 cfs / 6.29 ft	09:30 CDT	1970 cfs / 5.87 ft
Richland	2.72 ft falling	—	—	2.33 ft
Bear Cr	158 cfs / 3.11 ft falling	—	—	88.7 cfs / 2.82 ft

St. Joe peak: 6.96 ft / 2260 cfs at 00:30 — a +2.15 ft / +1538 cfs total event rise from 4.81 ft / 722 cfs baseline. Mid-Optimal range; 28% of flood threshold (8000 cfs).

Harriet peak: 6.29 ft / 2430 cfs at 09:30 — a +1.47 ft / +1456 cfs total event rise from 4.82 ft / 974 cfs baseline. Mid-Optimal; 26% of flood threshold (9370 cfs).

1. RAINFALL-RESPONSE PAIRS — final Event 8 transfer functions:

2. St. Joe (wet antecedent, watershed-wide): Pulse 2 zone-avg ~1.03" with hotspots 1.4-1.7". From storm centroid (~Day 59 13-19 CDT) to St. Joe peak (Day 61 00:30): ~30-35 hr lag. Transfer: +2.15 ft / 1.03" zone-avg = 2.1 ft/in (or +1538 cfs / inch). This is meaningfully higher than prior estimates and reflects the compound effect of two pulses on saturated antecedent.

3. Harriet: Same forcing → peak Day 61 09:30. Lag from storm centroid: ~38-44 hr. Transfer: +1.47 ft / 1.06" zone-avg = 1.4 ft/in. Lower than St. Joe per-unit because Harriet integrates a larger drainage area with more attenuation.

4. St. Joe → Harriet (this event): Peak-to-peak lag = 9 hr (00:30 → 09:30). Cleaner than prior estimates (which were 6-8 hr forecast). With wet conditions and channel already conveying ~2000 cfs, this is the empirical wet-condition value.

5. DOWNSTREAM PROPAGATION — full cascade now closed: Boxley peak (Day 60 00:30) → Ponca peak (Day 60 02:45, +2.25 hr) → Pruitt peak (Day 60 10:15, +7.5 hr) → St. Joe peak (Day 61 00:30, +14.25 hr) → Harriet peak (Day 61 09:30, +9 hr).

6. Pruitt→St. Joe: ~14.25 hr peak-to-peak (within prior 12-15 hr estimate; locks in the upper end at ~14 hr for compound wet-pulse events).

7. Total Boxley-to-Harriet propagation: ~33 hr peak-to-peak.

8. MULTI-DAY EVENT — Event 8 closure: Event 8 started Day 58 (Apr 27), final pulse Day 59 (Apr 28), recession through Day 60-61. All five mainstem gauges peaked sequentially. No flood threshold crossed at any gauge. Maximum tier classification: solid Tier 2 watershed-wide. Total recession from peak at St. Joe in 22 hr: -0.87 ft / -730 cfs (~0.04 ft/hr — typical large-river recession). Harriet recession from peak: -0.42 ft / -460 cfs in 13 hr.

9. ANOMALIES OR SURPRISES:

10. Pruitt→St. Joe lag of 14.25 hr is on the long end. This is interesting given that the mid-event storm contributed direct rain into the St. Joe zone (1.0+ inch over 14 HUC12s), which should have produced an internally-sourced pulse arriving earlier at St. Joe than the upstream propagation. But the St. Joe peak is single-peaked and clearly delayed — suggesting that the watershed-wide rainfall produced a coherent integrated peak rather than separate internal-vs-upstream pulses. The 1342 km² St. Joe zone effectively acts as a low-pass filter when forcing is uniform.
11. Harriet event peak (6.29 ft) closely matches forecast (6.3-6.5 ft). Forecast skill for downstream gauges is improving as the transfer functions calibrate.
12. Event 8 final cfs/in transfer ratios are notably high (St. Joe 2.1 ft/in zone-avg, Harriet 1.4 ft/in). These are wet-saturated, two-pulse compound conditions and should be filed as upper-bound transfer functions.

Local knowledge calibration: All recession-time observations continue to fit. Hailstone never reached Optimal (4.4 ft) — peak 4.10 ft was solidly low/floatable. Time above 3.7 ft Hailstone activation: ~13.5 hr total. Upper Richland time above 3.2 ft: ~14 hr (Day 59). Both fit "almost never more than 24 hours" and "rarely more than 24 hours" respectively.