How the Rahway River floods Millburn
A two-dimensional rain-on-grid model of Millburn Township and the upstream Rahway watershed, run for 9storms: NOAA design storms, the hurricanes that flooded downtown, and extreme what-ifs.
Open the interactive dashboardRead the reportsUncalibrated screening model
Ida 2021 in the model
Hurricane Ida remnants, 1-2 Sep 2021 (AORC observed rainfall).
All scenarios
Flooded areas cover the area of interest. Click through to the dashboard for maps and hydrographs.
| Scenario | Rain (in) | Peak flow, Millburn downtown (cfs) | Peak flow, Rahway R. nr Springfield (cfs) | Flooded > 0.3 m (km²) | Flooded > 1 m (km²) | Built-up > 0.3 m (km²) |
|---|---|---|---|---|---|---|
| Design storms | ||||||
| 2-year2-year 24-hour design storm (Atlas 14, NRCS Type III) | 3.4 | 810 | 2,094 | 1.58 | 0.17 | 0.07 |
| 10-year10-year 24-hour design storm (Atlas 14, NRCS Type III) | 5.1 | 2,221 | 4,889 | 4.30 | 0.88 | 0.25 |
| 100-year100-year 24-hour design storm (Atlas 14, NRCS Type III) | 8.5 | 6,333 | 11,960 | 7.56 | 3.81 | 0.75 |
| 500-year500-year 24-hour design storm (Atlas 14, NRCS Type III) | 11.7 | 11,276 | 18,824 | 9.81 | 5.54 | 1.27 |
| Historical (observed) | ||||||
| Floyd 1999Hurricane Floyd, 15-17 Sep 1999 (AORC observed rainfall) | 8.4 | 2,484 | 7,079 | 5.13 | 2.76 | 0.28 |
| Irene 2011Hurricane Irene, 27-29 Aug 2011 (AORC observed rainfall) | 8.5 | 3,653 | 9,286 | 6.07 | 3.26 | 0.47 |
| Ida 2021Hurricane Ida remnants, 1-2 Sep 2021 (AORC observed rainfall) | 7.3 | 7,522 | 16,092 | 8.06 | 4.37 | 0.96 |
| Extreme what-ifs | ||||||
| Ida, core over watershedIda with its wettest core (within ~60 km) transposed over the Rahway headwaters | 9.7 | 11,087 | 21,941 | 9.61 | 5.74 | 1.27 |
| Ida ×1.5Ida rainfall x1.5 (stress test) | 11.0 | 13,433 | 28,429 | 10.41 | 6.23 | 1.49 |
Gauges
The model reports discharge and depth at 6 points along the Rahway branches and Canoe Brook. The USGS gauge near Springfield is the one to calibrate against.
- Millburn downtown6.8 mi²
- Rahway W. Br. at Glen Ave (Short Hills)5.6 mi²
- Rahway W. Br. at Millburn/Springfield line15.2 mi²
- Rahway E. Br. at Maplewood6.5 mi²
- Canoe Brook9.8 mi²
- Rahway R. nr Springfield24.6 mi²
Reading the numbers
Design storms (2 to 500-year) use NOAA Atlas 14 24-hour depths with the NRCS Type III distribution. Historical storms replay NOAA's hourly gridded rainfall, and the what-ifs scale Ida or move its wettest core over the Rahway headwaters.
The model has not been calibrated, so treat it as a way to rank storms and compare interventions, not as a forecast of depths at a particular address.