The overall probability for that flooding will occur each year in Valley County is highly likely and its relative impact is high, and thus the overall risk for Valley County is high. The risk of flooding for each of the cities is different and was determined based upon the specific data collected and outlined in the history section of this hazard profile. In assessing flood data for the 2015 update, data from 2009 to 2014 was used to determine the risk for each of the cities and the county as a whole. Most notable are the cities of Glasgow, Nashua and the unincorporated areas of Valley County because they are at a high risk and have an extensive history of problematic flooding. The table provided below provides the name of each of the cities in the county, the probability that flooding will have an impact on that jurisdiction, the impact potential, as well as the overall risk calculated by the determine probability and impact ratings.
Table 45: Flood Hazard Risk Assessment
Flood
|
City
|
Probability
|
Impact
|
Risk
|
Glasgow
|
Possible
|
Very High
|
Very High
|
Fort Peck
|
Unlikely
|
Low
|
Little to No
|
Nashua
|
Highly Likely
|
Moderate
|
Moderate
|
Opheim
|
Possible
|
Low
|
Little to No
|
Valley County*
|
Highly Likely
|
High
|
High
|
Total
|
Highly Likely
|
High
|
High
|
The probability is based upon data available from 1996-2014
*Valley County information takes into account unincorporated areas of the County.
The 2015 update utilized the Risk = Frequency x Consequence (R = FC) formula and each jurisdiction has its own unique risk score based on the 28 points of data analyzed. The risk determined for the 2015 update represents little change from the previous plan, as the overall risk was high for the 2015 update. Similarly, the last plan update was completed in 2008 and indicated that flooding had the potential to have a high impact on Valley County.
4.4.2 Flood History in Valley County
The National Centers for Environmental Information’s Storm Events Database provided data on flood and flash flood events in Valley County. The data available was from June 1996 until July 2015. During this time period, there have been 82 events reported in Valley County. Of these 82 events, 51 occurred in the past five years in Valley County. The most recent flood events occurred in August and September of 2014. There were a flood and flash flood events reported at nine locations throughout Valley County. The flooding events which occurred in Valley County in August 2014 caused over $1 million in property damage. The following narratives outline the significant flood events.
-
On August 24, 2014, in Glasgow, a very wet and slow-moving low-pressure system stalled over Montana and directed near-continuous rainfall over central and northeastern portions of the state for several days. Rainfall totals ranged from 5 to 10 inches in the affected area. Valley County damages reported by DES to FEMA were in excess of $1.12 million dollars including the cost of repairs and labor. There were 36 locations across Valley County that was damaged (road, bridge, and culverts). On October 9th, 2014 a presidential disaster declaration was granted for this event. Heavy rainfall in the basin with amounts ranging from 4 to 10 inches over a four day period caused significant flooding in all the streams in the basin, and eventually the rivers. Willow Creek, Antelope Creek, Cherry Creek, Larb Creek, Brazil Creek all flooded during this time frame, blocking off many gravel roads around the county. Willow Creek Road from Fort Peck to the Pines had a very large area completely wiped out with a large culvert gone. No crop damage, injuries or deaths were reported as part of this event.
-
On August 24, 2014,inGlasgow, there was a flash flood event. Widespread heavy rainfall from preceding days along with embedded thunderstorms led to flash flooding in the Cherry Creek Basin. The initial report of flash flooding came from an NWS employee who reported that Cherry Creek on the northwest side of Glasgow has risen out of its banks and is flooding with several inches of water over Skylark Road at Martin Coulee. The Creek was actually flooding in the area about 4 miles north of Glasgow westward and then southward to the Milk River. Many homeowners evacuated and had to move livestock and trailers out of the flooded waters. This is the second highest the river has been in at least 4 decades (2011 was higher). There were over a dozen homes with water in the basements and crawl spaces, and the water was so high, many people were unable to leave their homes because the driveways were flooded over with swift moving water. There was a total of $150,000 in property damage as a result of this flash flood event. There were no reports of deaths, injuries or crop damage.
-
Starting late on August 22, 2014, widespread rainfall started statewide. The rain was almost continuous across portions of the state through August 25. Record rainfall totals for a 24 hour period, 46 hours and 72 hour and monthly period were common. Many locations had their wettest August on record, and some locations had the wettest ever as well. Most areas in the impacted region had at least 400% of normal, and the Saco, MT area had over 1000% of normal rainfall for the month. The Milk River at Glasgow had the worst flooding for this river. Several tributaries come into the Milk River in this region, and a dam break on Willow Creek contributed to additional flows of water coming into the main stem river and bringing the crest higher than anticipated originally. The Milk River at Glasgow rose quickly and went above flood stage near 11 pm on August 24 and receded around 6 am on September 4. The river peaked at 31.75 feet on August 26 which is the 14th highest crest on record. Impacts included:
• Whately Road having water across it east of Glasgow
• Livestock and Feedlots near the Milk River were isolated
• 6th Ave South and Rahlf Lane flooding
• Water covered Sullivan Park and softball/baseball fields
• Some driveways underwater near the river
The December 2015 System Wide Infrastructure Framework (SWIF) plan for the City of Glasgow Cherry Creek Left Bank and Milk River Left Bank Levee System stated that according to the National Oceanic and Atmospheric Administration records, the Milk River at Glasgow has experienced 26 crests over 30 feet which are 5 feet above flood stage. There are 20 events where the flood stage was over 31 feet which are considered major flooding. Since 1938, the 5 most significant floods include 2011, 1952, 1986, 1939 and 1978 (there are listed bythe highest crest in descending order). Overtopping of the Glasgow-Cherry Creek Lower Bank and Milk River Lower Bank levee surrounding Glasgow and the Tampico Highway at the Burlington Northern Santa Fe railroad on 2nd Avenue South would not occur until a crest of 35 feet is reached.
Location
|
County/Zone
|
St.
|
Date
|
Time
|
T.Z.
|
Type
|
Mag
|
Dth
|
Inj
|
PrD
|
CrD
|
Totals:
|
|
|
|
|
|
|
|
0
|
0
|
1.271M
|
0.00K
|
DUCK CREEK
|
VALLEY CO.
|
MT
|
05/27/2010
|
21:00
|
MST-7
|
Flash Flood
|
|
0
|
0
|
1.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
07/28/2010
|
19:44
|
MST-7
|
Flash Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
03/23/2011
|
11:38
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
04/04/2011
|
03:21
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
04/05/2011
|
12:02
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
TAMPICO
|
VALLEY CO.
|
MT
|
04/06/2011
|
08:54
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
04/07/2011
|
00:04
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
NASHUA
|
VALLEY CO.
|
MT
|
04/08/2011
|
12:02
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
04/13/2011
|
21:28
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
VANDALIA
|
VALLEY CO.
|
MT
|
04/21/2011
|
21:21
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
NASHUA
|
VALLEY CO.
|
MT
|
05/01/2011
|
00:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
05/01/2011
|
00:01
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
05/10/2011
|
11:04
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
05/10/2011
|
23:08
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
05/11/2011
|
08:26
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
05/18/2011
|
05:21
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
05/20/2011
|
09:19
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
05/22/2011
|
06:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
NASHUA
|
VALLEY CO.
|
MT
|
05/23/2011
|
16:45
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
VANDALIA
|
VALLEY CO.
|
MT
|
05/25/2011
|
13:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
05/30/2011
|
19:48
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
06/01/2011
|
00:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
NASHUA
|
VALLEY CO.
|
MT
|
06/01/2011
|
00:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
06/01/2011
|
00:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
TAMPICO
|
VALLEY CO.
|
MT
|
06/01/2011
|
00:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
OSWEGO
|
VALLEY CO.
|
MT
|
06/05/2011
|
13:16
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
06/07/2011
|
08:20
|
MST-7
|
Flash Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
BLUFF CREEK RAWS
|
VALLEY CO.
|
MT
|
06/07/2011
|
15:22
|
MST-7
|
Flash Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW INTL AIRPORT (KGGW)
|
VALLEY CO.
|
MT
|
06/07/2011
|
15:45
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
SAINT MARIE
|
VALLEY CO.
|
MT
|
06/11/2011
|
15:11
|
MST-7
|
Flash Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
SAINT MARIE
|
VALLEY CO.
|
MT
|
06/11/2011
|
16:57
|
MST-7
|
Flash Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
06/11/2011
|
19:35
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
SAINT MARIE
|
VALLEY CO.
|
MT
|
06/17/2011
|
12:25
|
MST-7
|
Flash Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
NASHUA
|
VALLEY CO.
|
MT
|
06/17/2011
|
22:37
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
KING COULEE RAWS
|
VALLEY CO.
|
MT
|
06/20/2011
|
20:21
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
PARK GROVE
|
VALLEY CO.
|
MT
|
07/01/2011
|
00:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
07/22/2011
|
14:03
|
MST-7
|
Flash Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
07/22/2011
|
14:26
|
MST-7
|
Flash Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
05/25/2013
|
18:25
|
MST-7
|
Flash Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
06/04/2013
|
19:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
06/04/2013
|
19:40
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
TAMPICO
|
VALLEY CO.
|
MT
|
06/06/2013
|
03:40
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
08/24/2014
|
05:00
|
MST-7
|
Flood
|
|
0
|
0
|
1.120M
|
0.00K
|
GLASGOW INTL AIRPORT (KGGW)
|
VALLEY CO.
|
MT
|
08/24/2014
|
06:25
|
MST-7
|
Flash Flood
|
|
0
|
0
|
150.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
08/24/2014
|
15:01
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
08/24/2014
|
21:50
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
TAMPICO
|
VALLEY CO.
|
MT
|
08/26/2014
|
06:16
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
NASHUA
|
VALLEY CO.
|
MT
|
08/26/2014
|
06:40
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
TAMPICO
|
VALLEY CO.
|
MT
|
09/01/2014
|
00:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
GLASGOW
|
VALLEY CO.
|
MT
|
09/01/2014
|
00:00
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
HINSDALE
|
VALLEY CO.
|
MT
|
09/03/2014
|
06:12
|
MST-7
|
Flood
|
|
0
|
0
|
0.00K
|
0.00K
|
Totals:
|
|
|
|
|
|
|
|
0
|
0
|
1.271M
|
0.00K
|
Martin Coulee Road Flooding
Residents on Martin Coulee road still have concerns over the increased frequency of flooding in the Martin Coulee drainage area. Recent history shows that the Billman Approach area has washed away three times, as well as portions of Martin Coulee road on the Campbell side. The new culvert on Billman's approach was damaged during the most recent event. One side of the culvert collapsedand now restricts the volume it was originally designed to handle. Roughly 48 loads of gravel have washed into the downstream side of this approach impeding the flow as well. This flooding can cause a damming issue and if suddenly released would impact Cherry Creek.
Essentially, there is now a mix of a man-made/nature made geographical change downstream of this approach. This has negated previous efforts to mitigate the risk of flooding up and downstream of this location.
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