PROJECT ALERT NOTICE (ND SD) Dakota WSC Flooding

Date: Wed, 27 Mar 2019 16:36:02 EDT

Summary: USGS response to flooding in SD & ND (Day 14).

Gage-heights at forty (40) U.S. Geological Survey streamgages in South Dakota (SD) and North Dakota (ND) are exceeding National Weather Service (NWS) minor to major flood stages. The distribution of the forty sites experiencing flooding in the Dakotas can be observed at the WaterWatch link below (please note that the use of multiple gage height sensors in ND prevents some sites from clearly displaying the presence of flood conditions in ND at the link below).

*Eastern SD - major flooding (7 locations) on the Big Sioux and James Rivers will continue for some time as melting snow continues to reinforce the current flows. No new PORs are currently forecast for either river, but some sites will remain near POR through at least the weekend. Flow in the diversion channel around Sioux Falls is at POR. Webcam imagery of the Sioux Falls area is available at https://siouxfalls.org/flood/webcams

*Central and Southwest SD - flows on the Keya Paha, Cheyenne, White, and Bad Rivers are still high but no longer rising. A wintry mix of precipitation is forecasted for southwest SD. The provisional annual exceedance probabilities (AEP) for stations with a high number of recorded peaks in each basin are:

06423500 CHEYENNE R. NEAR WASTA, SD (92 peaks) 0.370 AEP or "2.7-year recurrence interval"
06452000 WHITE R. NEAR OACOMA,SD (91 peaks) 0.033 AEP or "31-year recurrence interval"
06464500 KEYA PAHA R AT WEWELA,SD (74 peaks) 0.027 AEP or "38-year recurrence interval"
06441500 BAD R NEAR FORT PIERRE,SD (94 peaks) 0.095 or "11-year recurrence interval"

*Northwest SD - flows on the Little Missouri have crested but the Grand and Moreau Rivers are still rising. The POR forecast for the Moreau River at Whitehorse (06360500) is still high but has been lowered several feet since yesterday.

*Western ND - the Yellowstone River nr Cartwright (06329610) has dropped below POR with the releasing of the ice jam. The Missouri River near Williston is at major flood stage. There is still significant snowpack present south of Bismarck, ND in the Cannonball and Beaver Creek Basins with peaks expected later this week for these basins.

*Eastern ND - major flooding is still forecasted, but little runoff has begun. A slow and gentle melt continues as temperatures oscillate above and below freezing from day to night. The NWS has indicated that river flooding is not likely to commence this week. One RDG has been deployed in the James River Basin. Seven more RDGs are being deployed this week in the Red River Basin.

More approximate annual exceedance probabilities (AEP) will be provided for various basins once the peaks have passed.

Since the beginning of flood conditions on March 13, 2019, USGS crews in the DWSC have made 129 measurements despite ice and overland flooding challenges. All data section staff in both states are deployed today to measure flows and repair gages. Three real-time sites are currently having operational issues. The White River near Kadoka, SD (06423500) streamgage was destroyed when it fell into the river after the bank scoured 40 ft. Many sites have damaged or lost CSGs.

Some photos from the field are available here (DOI access only): https://drive.google.com/drive/folders/1bNiqh_sBAegZgSJQyocSZ2skHDlsJkVf?usp=sharing

The Dakota WSC Facebook page has also been updated with recent flood information: https://www.facebook.com/USGSDakotas/

Stakeholders are being informed of our activities through updates to NWISWeb, NWSChat, email, and phone calls.

Dakota WSC Flood Map