PROJECT ALERT NOTICE (ND SD) Dakota WSC Flooding

Date: Fri, 12 Apr 2019 15:14:34 EDT

Summary: USGS response to flooding in SD & ND (Day 30).

Bottom line up front: The second "Bomb Cyclone" of the spring season delivered a broad swath of 20-24 inches of snow across SD. Snow will melt quickly next week resulting in new flood crests late next week and into the following week. Hazardous winter conditions will limit almost all fieldwork today. Three crews working outside the storm impact areas will work their way home today or tomorrow as road conditions allow. All but one crew will be off this weekend. Project alerts will resume next Monday (April 15).

Gage-heights at thirty-eight (38) U.S. Geological Survey streamgages operated by the Dakota WSC in South Dakota (SD), North Dakota (ND), and Minnesota (MN) are exceeding National Weather Service (NWS) minor to major flood stages. The distribution of the thirty-eight sites experiencing flooding can be observed at the WaterWatch link below.

Eastern ND - Snow is still falling with up to a foot of new snow in the southern Red River Basin. The additional moisture will cause secondary peaks on smaller tributaries of the Red River and slow the recession on the main stem Red River. Nine locations in the Red River Basin are currently at major flood stage. The confluence of the Rush (receding), Maple (receding), and Sheyenne Rivers (peaking) just north of Fargo is resulting in a broad area of overland flooding that has not yet receded. The confluence of some tributaries with the swollen Red River is resulting in feet of backwater at a few locations (-14.5ft. at 05069000 Sand Hill River at Climax). The peak on the Red River at Fargo occurred April 8 at a provisional value of 35.03 ft. with 19,500 cfs. The annual exceedance probability (AEP) is 0.04 ("25-year recurrence interval"). The Red River at Grand Forks, ND appears to have peaked yesterday at between 46-47 ft. Links to data and imagery for the Red River Basin are provided below:

USGS installed a webcam at Fargo, ND with real-time imagery available at https://cida.usgs.gov/stormsummary/timelapse/BasicData/DakotaWSC/DWSC/DAK_Red_River_Fargo_timelapse_videos/frame_gallery/

USGS photos from the field are added daily to (DOI access only) https://drive.google.com/drive/folders/1bNiqh_sBAegZgSJQyocSZ2skHDlsJkVf?usp=sharing

See time-lapse photos of an ADCP measurement here https://www.facebook.com/USGSDakotas/videos/368820610386931/

SD - Attention will be focused on much of SD next week as isolated pockets of heavy snow could result in flashy peaks in the steeper gradient western SD. Moving eastward the response to snowmelt will be slower due to the deeper snowpack and flat topography but last longer. The James and Big Sioux Rivers are already at moderate to major flood stage and are expected to respond to the melting of this newest snow by late next week. Eight of nine locations on the James are still at major flood stage.

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 474 (9 yesterday) measurements despite ice and overland flooding challenges. High stages in the shallow gradient of the James, Big Sioux, and Red Rivers are resulting in extensive (miles in some cases) submerged floodplains, road overflow, and substantial shifts from the stage-discharge ratings. Hazardous winter conditions will limit almost all fieldwork today. Eight RDGs deployed in eastern ND are operational. The storm has resulted in telemetry loss at half a dozen streamgages today. New infrastructure damage from ice is declining in the flooded area. Crews are actively documenting high water marks. Nine water-quality samples have been collected in flooded areas since March 13, 2019. Three indirects scheduled for this week were canceled due to the storm. Stakeholders are being informed of our activities through updates to NWISWeb, NWSChat, email, and phone calls.

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


Dakota WSC Flood Map