PROJECT ALERT NOTICE (ND SD) Dakota WSC Flooding

Date: Mon, 25 Mar 2019 16:07:54 EDT

Summary: USGS response to flooding in SD & ND (Day 12).

Gage-heights at fifty (50) 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 fifty 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).

Significant new or ongoing issues since the project alert from yesterday include:
-POR conditions on the Moreau River in northwest SD and Yellowstone River in northwest ND.
- Continued high flows on the White and Cheyenne River in central and southwest SD.
-Ongoing slow-motion major flooding in eastern SD on the Big Sioux and James Rivers.
-The loss and recovery of a RiverPro ADCP.

Two real-time stations are available on the Moreau River with the upstream stationing appearing to crest today. Crews are at the downstream station currently and have found a provisional HWM that exceeds by 1 foot the previous peak gage height set in 1997 (63 years of record). The Yellowstone River nr Cartwright, ND is reporting POR conditions with NDDOT reporting, "Highway 200 near Cartwright (mile point 2) to the Highway 58 Junction closed until further notice due to water over the road." Previous POR occurred in 1978. Flooding on the Yellowstone is likely the result of ice jamming.

USGS 06329610 YELLOWSTONE R NO. 2 NR CARTWRIGHT, ND (stage only)
https://waterwatch.usgs.gov/?id=wwsa&site_no=06329610

Widespread high flows continue in central and southwest SD. High flows on the Keya Paha are rapidly receding, but the White River is still near peak flows. Sites with shorter records have POR conditions. Stations with longer records are indicating similar conditions existed in 1952, 1960s, and the late 90s. Significant flooding in the Sioux Falls, SD area is occurring, but the Big Sioux River near Dell Rapids (just upstream of Sioux Falls) is now forecasted to have a broader peak that is slightly below POR.

USGS 06481000 BIG SIOUX R NEAR DELL RAPIDS, SD
https://waterwatch.usgs.gov/?id=wwsa&site_no=06481000

With webcam imagery of the Sioux Falls area is available at https://siouxfalls.org/flood/webcams

A RiverPro ADCP was lost yesterday afternoon on the White River nr Oacoma after the rope tethering the trimaran broke when the boat dove under the water. A search and recuse effort launched from the Missouri River today recovered the unit, visually undamaged, about four miles downstream of the gage. Thank you to all the WSCs that offered the assistance of additional acoustic equipment.

Since the beginning of flood conditions on March 13, 2019, USGS crews in the DWSC have made 89 measurements despite ice and overland flooding challenges. All data section staff in both states are deployed today to measure flows and repair gages. Four PORs occurred yesterday with two occurring at sites with over forty years of record. There are likely more POR at CSG sites. Nine real-time sites are currently having operational issues and many CSGs have been destroyed.

The DWSC has been in contact with the Office of Communications. A live radio interview was conducted with SD Public Radio today. A local ABC affiliate TV crew met with a field crew in Sioux Falls today as well. Stakeholders are being informed of our activities through updates to NWISWeb, NWSChat, email, and phone calls.

Dakota WSC flood map.