Strong thunderstorms produced torrential rainfall in Cataract and Havasu Canyons. (The name of the creek changes name at Supai Springs.) The flash flood caused evacuations,  extensive campground damage, and lose of camper's belongings.

Flash Flood in COCONINO, ARIZONA
From 11-JUL-18 19:30:00 to 11-JUL-18 21:30:00 (MST-7)
Location: HAVASUPAI
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Two flood waves hit the Supai area late on July 11th.  The first (and most damaging) occurred around 7-7:30 pm (the other later that night).  Serious flooding occurred in the Supai campground, with reports of a 7��� rise in the stream in the area. Campers were displaced, tents and belongings swept away, and some campers stranded in trees. Visitors (150-200) were evacuated from the campground, and taken from the canyon the next day. No serious injuries reported.  No damage was reported in the Village of Supai.
The reports of a ���7 foot wall of water��� hitting the area is consistent with gauge data, with a 4��� rise at the Supai Gauge (850 CFS), and an 8��� rise downstream at the Colorado River (3760 CFS).
At 5:30 PM: Heavy Rainfall.  Radar est 1 - 1.5 rain fell in the Supai area between 5:30pm and 630pm.
Storms moving from SE to NW.  KICX estimates 1-1.5��� of rain fell a few miles upstream of the USGS gauge in about an hour, from 530 pm  to 630 pm.  In addition, about 1-1.5��� of rain fell over and just downstream of Supai Village in about 40 minutes, between 550 pm and 630 pm).

Between 7:00-7:30 PM:  It is estimated that the flooding began in the campground area between 7 and 7:30 PM.  A flood crest with a 4��� rise (800 CFS) hit the Supai Gauge (upstream from the campground) at 7:30 pm.
It is important to note that most of the rain impacting the camping area fell downstream of the Supai gauge...the 4��� rise at the does not accurately represent the impacts at the camping area.  Downstream gauge at the Colorado River recorded 8��� rise with 3760 CFS.
10:30 PM:  First call from Supai (Peach Springs dispatch) of flood situation.  (verify time?)
On July 12: at 12:00 AM, additional storms developed over and just south of Supai - with an additional 1 of rain falling upstream of the campground between approximately 12:00 and 1:00 AM.
At 2:00 AM:  Gauge at Supai rose above flood stage again at 2 am (4.5' rise, 1700 CFS).
It is clear by the distribution of the rainfall that the campground flooding was not ���caught��� by the Supai gauge - the heaviest rainfall fell downstream of the stream gauge (and over, or just upstream of the campground area).  The Cataract Creek at Heather Wash and Topocoba Gauges recorded minor rises associated with the passing of the storm.
Tracking the surge(s) between the two Havasu stream gauges, it appears that it took about 2.5 hours for the surges (flood crests) to go from the Supai gauge location to the mouth at the Colorado River.
At 730 PM, the gauge on Havasu Creek at Supai measured a 4��� rise, 846 CFS. At 745 PM MST,  the gauge on Havasu Creek at the Colorado River Mouth (Co river) measured a 8.5��� rise, 3760 CFS.
Secondary, minor rise associated with ���Supai��� surge above measured a 0.7��� rise, 300 CFS increase) at 1000 PM MST.

Flash Flood in COCONINO, ARIZONA
From 12-JUL-18 02:00:00 to 12-JUL-18 06:00:00 (MST-7)
Location: HAVASUPAI
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

The stream gauge at Supai showed a rapid rise on Havasu Creek at 200 AM.