Event 3 has begun. A moderate rainfall event occurred across the watershed overnight and into the early morning hours of March 11. Rain was concentrated in the upper watershed (Boxley, Ponca, Pruitt zones) with diminishing totals moving downstream and east.
Spatial distribution by gauge zone (24-hr totals): | Zone | Total 24hr (avg) | Peak 1hr | Peak Time (UTC) | Notes | |------|-----------------|----------|-----------------|-------| | Ponca | 0.826" | 0.620" | 07:06 (01:06 CST) | Heaviest zone — Smith Creek 0.984" | | Boxley | 0.811" | 0.390" | 07:06 (01:06 CST) | Strong headwater rain | | Richland | 0.565" | 0.216" | 08:06 (02:06 CST) | Moderate | | Pruitt | 0.526" | 0.254" | 07:06 (01:06 CST) | Moderate — local + upstream | | Bear Creek | 0.518" | 0.201" | 08:06 (02:06 CST) | Moderate | | St. Joe | 0.505" | 0.294" | Various | Distributed across 14 HUC12s | | Harriet | 0.333" | 0.133" | 09:06 (03:06 CST) | Lightest gauged zone |
Key HUC12 hotspots: - Smith Creek (0203, Ponca zone): 0.984" with 0.620"/hr peak — the highest single-HUC12 total - Beech Creek (0202, Ponca zone): 0.821" with 0.381"/hr peak - Boxley headwaters (0201): 0.811" with 0.390"/hr peak - Whiteley Creek (0205, Ponca zone): 0.672" with 0.362"/hr peak - Cave Creek (0305): 0.645" with 0.271"/hr peak - Headwaters LB (0102): 0.635" with 0.249"/hr peak
Temporal pattern: The rain was concentrated in a ~3-6 hour window, primarily 01:00-04:00 CST (07:06-10:06 UTC). Peak intensities in the upper watershed (Boxley, Ponca) occurred around 01:06 CST; further east/south (St. Joe tributaries, Bear Creek) peaks were ~1-2 hours later (02:06-03:06 CST), indicating a frontal system moving generally west-to-east.
Antecedent conditions: Very wet — 7-day precip ranges from 1.5-3.3" across the watershed, with the heaviest antecedent in the upper watershed (Cove Creek 3.27", Whiteley Creek 3.22", Beech Creek 2.78"). Soils remain substantially saturated from Events 1 and 2.
This is a well-defined Event 3, with clear responses at Boxley, Ponca, and Pruitt. Downstream gauges (St. Joe, Harriet) are still on the Event 2 recession limb, and today's rain has modulated but not yet clearly spiked those gauges.
Boxley (07055646): - Pre-event baseline: 2.62 ft (still elevated from Event 2; original baseflow was 1.90 ft) - First detectable rise: ~01:45 CST (2.63→2.68 ft, +0.05 ft in 15 min) - Peak: 3.28 ft at ~11:45-12:00 CST - Total rise: +0.66 ft - Rise rate: Max 0.15 ft/hr at 05:00 CST; the rise was smooth and sustained over ~10 hours - Now in recession: 3.03 ft at EOD, falling at ~0.02 ft/hr - Local knowledge comparison: At 3.28 ft, the Boxley-to-Ponca section was above Optimal (threshold 3.7 ft not reached). The Boxley gauge was above the Low-but-Floatable threshold (3.2 ft) for approximately 2 hours (roughly 10:15-12:15 CST). It's now at 3.03 ft, below 3.2 ft.
Ponca (07055660): - Pre-event: 197 cfs (just below Low-Floatable threshold of 200 cfs — had been right at the boundary) - First detectable rise: ~02:00 CST (197→202 cfs) - Peak: 547 cfs at ~08:45-09:00 CST - Total rise: +350 cfs (+178%) - Now in recession: 344 cfs at EOD, well within Optimal range (200-1,600) - Duration in Optimal: From ~02:00 CST onward — still Optimal at EOD (22+ hours and counting)
Pruitt (07055680): - Pre-event: 4.51 ft / 308 cfs (still elevated from Event 2) - Two-phase response observed: - Phase 1 (local Pruitt-zone rain): Small initial rise from ~02:45 CST, 4.53→4.63 ft by 06:00 CST (+0.10 ft). This corresponds to the ~0.53" of local Pruitt-zone rain (Cove Creek 0.508", Hoskin Creek 0.545") - Phase 2 (Ponca flood wave arrival): Dramatic acceleration beginning ~11:00 CST, with the fastest rise 0.42 ft/hr at 13:45 CST. The gauge surged from 4.93 ft at 11:00 to 5.93 ft at 16:15 (+1.00 ft in ~5.25 hours) - Peak: 5.93 ft / 857 cfs at ~16:15 CST - Total rise: +1.42 ft / +549 cfs - Now in early recession: 5.67 ft / 741 cfs at EOD - Recreational status: Optimal (200-2,000 cfs) throughout the day. Never approached Flood threshold. - Pruitt gauge precip: 0.51" — consistent with zone QPE
St. Joe (07056000): - Continued Event 2 recession through most of the day: 891 cfs at 00:00 → 791 cfs at ~19:45 CST (continued decline of ~4-5 cfs/hr) - Recession halt/reversal detected late in the day: Starting ~21:00 CST, St. Joe stopped falling and began a slight rise: 796→807 cfs by 22:45 CST (+0.03 ft height rise from 5.02→5.05 ft) - This is consistent with the leading edge of the Pruitt flood wave arriving (Pruitt peaked at ~16:15 CST; Pruitt→St. Joe lag from Event 2 was ~14 hours, so the main pulse should arrive ~06:00 CST on 3/12) - Also: St. Joe received 0.34" locally (gauge precip), plus ~0.5" across its 14 HUC12s. Some of this contributed to arresting the recession, but the main rise has yet to arrive. - Recreational status: Optimal (200-8,000 cfs) throughout
Harriet (07056700): - Continued steady recession: 1,130 cfs at 00:00 → 933 cfs at EOD - Recession rate: ~8.2 cfs/hr, consistent with Phase 2 baseflow recession - No response to today's rain yet — this is expected given ~21-27 hour lag from Pruitt - Recreational status: Optimal (200-9,370 cfs) throughout - Harriet gauge precip: only 0.08"
Richland Creek (07055875): - Minimal response despite 0.565" average across Richland HUC12s - Brief spike to 1.77 ft at ~08:45-09:00 CST from 1.72 ft (+0.05 ft), then settled back to 1.71-1.73 ft - This confirms that ~0.5-0.6" in the Richland sub-basin produces only a marginal, transient response - Richland is at 1.71 ft — still far below the 3.2 ft recreational threshold
Bear Creek (07056515): - No meaningful response despite 0.518" across Bear Creek HUC12s - Remained at 2.56-2.59 ft / 19.2-21.0 cfs all day - Bear Creek gauge precip: 0.11" (much less than the zone average, suggesting the rain was more in the headwaters)
Pair 3a: Boxley headwaters → Boxley gauge - QPE: 0.811" in HUC12 0201, peak 0.390"/hr at ~01:06 CST - Response: +0.66 ft rise, beginning ~01:45 CST, peaking ~11:45 CST - Lag (rain peak to gauge peak): ~10.5 hours - Antecedent: Very wet (2.41" 7-day). Pools partially filled from Event 2 (gauge at 2.62 ft vs 1.90 ft baseflow) - Comparison to Events 1 & 2: - Event 1 (dry antecedent, 1.038"): +0.87 ft, ~9-10 hr lag - Event 2 (moderately wet, 1.135"): +0.81 ft, ~10 hr lag - Event 3 (wet antecedent, 0.811"): +0.66 ft, ~10.5 hr lag - Key finding: Despite wetter antecedent conditions, the response was SMALLER than Events 1 and 2, proportional to the lower rainfall total. The lag time is remarkably consistent at ~10 hours across all three events regardless of antecedent conditions. This suggests the pool-and-drop system has a characteristic residence time of ~10 hours that is relatively insensitive to saturation state. - Transfer ratio: 0.811" → 0.66 ft = 0.81 ft/inch. Compare: Event 1 = 0.84 ft/inch, Event 2 = 0.71 ft/inch. These are converging around 0.75-0.85 ft per inch at Boxley. Confidence: Moderate (3 events, consistent range).
Pair 3b: Ponca zone → Ponca gauge - QPE: 0.826" average across 3 HUC12s (Smith Creek 0.984", Beech Creek 0.821", Whiteley 0.672") - Response: +350 cfs (197→547 cfs, +178%) - Lag (rain peak ~01:06 CST to gauge peak ~08:45 CST): ~7.5 hours - Antecedent: 197 cfs (well above 83.7 cfs baseflow — still 2.4x elevated from Event 2) - Comparison to Events 1 & 2: - Event 1 (dry, ~0.7" zone avg): +95 cfs - Event 2 (wet, 1.918" zone avg): +1,975 cfs - Event 3 (very wet, 0.826" zone avg): +350 cfs - The response amplitude scales non-linearly with rainfall. The Event 2 response was disproportionately large because it received ~2.3x the rain of Event 3 but produced ~5.6x the discharge rise. This is consistent with threshold-based runoff generation.
Pair 3c: Ponca flood wave → Pruitt gauge (propagation) - Ponca peaked at ~08:45 CST (547 cfs) - Pruitt began its dramatic acceleration at ~11:00 CST and peaked at ~16:15 CST - Lag (Ponca peak to Pruitt peak): ~7.5 hours - Flow conditions: 300-550 cfs transit flow - Comparison: Event 1 (low flow ~150 cfs) had Ponca→Pruitt lag of ~15-16 hours. Event 2 (flood flow ~2,000 cfs) had lag of ~5.75 hours. Event 3 at ~400-500 cfs: 7.5 hours. - This gives us a third data point for the velocity-vs-discharge relationship in the Ponca→Pruitt reach: - ~150 cfs → ~15 hr lag → ~0.46 m/s - ~500 cfs → ~7.5 hr lag → ~0.93 m/s - ~2,000 cfs → ~5.75 hr lag → ~1.2 m/s - Velocity ∝ Q^0.35 fits these three points reasonably well (√Q would predict too fast at low flows). Will refine with more data.
The Event 3 flood wave is currently between Pruitt and St. Joe:
| Gauge | Peak Time | Peak CFS | Status at EOD |
|---|---|---|---|
| Ponca | ~08:45 CST 3/11 | 547 | Receding (344 cfs) |
| Pruitt | ~16:15 CST 3/11 | 857 | Receding (741 cfs) |
| St. Joe | Not yet peaked | — | Recession arrested; slight rise starting ~21:00 CST |
| Harriet | Not yet peaked | — | Still in Event 2 recession |
Expected timing for St. Joe peak: Based on Event 2 Pruitt→St. Joe lag of ~14 hours, and adjusted downward slightly for the moderate flow conditions (~800 cfs vs ~2,600 cfs in Event 2), the St. Joe peak should occur approximately March 12 at 04:00-08:00 CST. The pulse will be attenuated by the large St. Joe drainage area, but it will also be supplemented by ~0.5" of local St. Joe zone rain.
The early arrest of St. Joe's recession at ~21:00 CST (5 hours after Pruitt peak) is consistent with the fast leading edge of the wave arriving. The main peak follows the crest.
Event 2 recession status (Day 4 — updated):
The Event 2 recession was proceeding smoothly until Event 3 interrupted it. This creates a "stacked event" situation:
| Gauge | Pre-Event 3 (3/11 00:00) | Current (EOD 3/11) | Event 3 Effect |
|---|---|---|---|
| Boxley | 2.63 ft | 3.03 ft | Event 3 added +0.40 ft above recession trend |
| Ponca | 197 cfs | 344 cfs | Event 3 reversed recession, now elevated |
| Pruitt | 315 cfs | 741 cfs | Event 3 doubled discharge |
| St. Joe | 891 cfs | 807 cfs | Still receding; Event 3 wave arriving |
| Harriet | 1,130 cfs | 933 cfs | Still receding; no Event 3 signal yet |
Key observation on stacked events: The pre-existing elevated baseflow from Event 2 means Event 3's rainfall (~0.5-0.8") produces responses that are proportionally larger than they would be from true baseflow. At Ponca, 0.83" of rain on an already-elevated system (197 cfs) produced a 547 cfs peak. Compare this to Event 1 where similar rainfall (~0.7-1.0") from true baseflow (83.7 cfs) only produced 179 cfs.
Recreational impact: This stacking effect is extending Optimal-or-better conditions substantially: - Ponca has been Optimal or better since Event 2 onset (March 7) — now 4+ days, with Event 3 ensuring at least another 2-3 days - Pruitt: 857 cfs peak from Event 3 ensures Optimal for at least 2 more days on top of the Event 2 tail - St. Joe: Has been in Optimal continuously since March 7 — now Day 5, with the Event 3 wave still arriving
1. Boxley lag time consistency (NOTABLE): The ~10-hour lag at Boxley has been remarkably consistent across three events with very different antecedent conditions (dry, moderate, wet). I hypothesized that wet antecedent conditions would shorten the lag (pre-filled pools), but the data shows the lag is essentially constant. This suggests the pool-and-drop residence time is dominated by the physical channel geometry (pool volume / throughput rate) rather than by how much water is already in the pools. The pools may primarily delay flow rather than store it — once they're topped up, additional inflow pushes out an equal volume at approximately the same rate. Confidence: Moderate (3 events).
2. St. Joe recession arrest provides propagation signal: The slight uptick at St. Joe starting ~21:00 CST, exactly 5 hours after Pruitt's peak, gives us a "first arrival" time for the wave front. The peak will follow later. This is useful — it means the leading edge of a flood wave from Pruitt arrives at St. Joe ~5 hours before the crest. For flood forecasting, this provides early warning.
3. Bear Creek non-response despite 0.5" rain: Bear Creek received ~0.52" across its HUC12s but showed essentially no response (0.03 ft total range). Compare to Event 2 where 1.2" produced a clear 0.59 ft / +42 cfs response. This refines the Bear Creek detection threshold upward: 0.5" is below detection at Bear Creek; the threshold is likely between 0.5-1.0". The Bear Creek watershed's larger area (239 km²) and likely deeper soils require more rain to generate detectable runoff. Confidence: Low-Moderate (2 events).
4. Pruitt two-phase response clearly distinguishes local vs upstream contribution: The initial gentle rise (Phase 1, +0.10 ft from local rain) followed by the dramatic Ponca wave arrival (Phase 2, +1.32 ft) provides clean separation of these two signals. At Pruitt, local rain (~0.53") contributed ~7% of the total rise while upstream propagation from Ponca contributed ~93%. This is a useful decomposition for understanding Pruitt's behavior.