Flash Flood and Flooding in Virginia, May 18 to 27, 2020

The Roanoke ASOS (ROA) set date rainfall records for three consecutive days: May 19, 20 and 21 with 2.84 inches, 2.76 inches and 2.72 inches, respectively. These were also the 5th, 6th and 7th wettest days in May in the period of climate data for Roanoke back to 1912. The 3-day total of 8.32 inches ending at midnight on the 21st was easily the highest on record in May. The previous 3-day record for May was 5.70 inches in 1940. For any 3-day period it was the 5th wettest on record, trailing August 14-16, 1940 with 9.31 inches. Per NOAA Atlas 14, for a 3-day period this rainfall total is in the 90 percent confidence interval (7.27 to 8.65 inches) for a 50-year recurrence event (.02 annual exceedance probability).

The CoCoRaHS site at Rocky Mount 2.2 NW (VA-FR-24) had a 4-day total of 11.86 inches of rain ending at 700 AM on May 22nd. Daily rainfall totals were 1.55, 3.67, 4.42, 2.22 inches starting on May 19th. Per NOAA Atlas 14, for a 4-day period this rainfall total is in the 90 percent confidence interval (10.7 to 12.9 inches) for a 200-year recurrence event (.005 annual exceedance probability).

The NWS Cooperative station at Rocky Mount (RYMV2) had its wettest May day on record with 3.25 inches for the 24-hour period ending 700 AM EST on May 21st. The previous May record was 3.15 inches on May 6, 1989. A 2-day record was also established ending 700 AM on the 21st with 6.00 inches , the previous record was 4.90 inches May 11-12, 1912. At 3-days a new record of 7.80 inches was set and at 4-days the 9.25 inch total was also a record. Prior to this event, the 4-day record for May was 4.98 inches set May 20-23, 1909. A broken period of record dates back to 1894 at this site. Per NOAA Atlas 14, for a 4-day period, the rainfall total of 9.25 inches is in the 90 percent confidence interval (8.60 to 10.1 inches) for a 50-year recurrence event (.02 annual exceedance probability).

The NWS Cooperative station at Copper Hill (COHV2) had its wettest 2-day period in May with 6.03 inches ending 700 AM EST on May 22nd. The previous May 2-day record (before this event) was 4.65 inches on May 16, 1942. May records for 3-day rainfall of 7.91 inches and 4-day rainfall of 8.92 inches were also achieved ending at 700 AM on May 22nd. Per NOAA Atlas 14, for a 3-day period this rainfall total is in the 90 percent confidence interval (6.84 to 8.16 inches) for a 25-year recurrence event (.04 annual exceedance probability) and at 4-days it was in the 90 percent confidence interval (8.16 to 9.74 inches) for a 50-year event (.02 annual exceedance probability). Complete data extends back to 1940 at this site.

The CoCoRaHS site at Copper Hill 6.2 S (VA-FL-2) had a 4-day total of 13.66 inches of rain ending at 700 AM on May 22nd. Daily rainfall totals were 2.46, 3.22, 4.80 and 3.18 inches starting on May 19th. Per NOAA Atlas 14, for a 4-day period this rainfall total is in the 90 percent confidence interval (12.2 to 15.0 inches) for a 500-year recurrence event (.002 annual exceedance probability).

The CoCoRaHS site at Roanoke 5.9 WSW (VA-RN-19) had a 4-day total of 11.34 inches of rain ending at 700 AM on May 22nd. Daily rainfall totals were 1.98, 2.74, 4.01, 2.61 inches starting on May 19th. Per NOAA Atlas 14, for a 4-day period this rainfall total is in the 90 percent confidence interval (10.4 to 12.6 inches) for a 500-year recurrence event (.002 annual exceedance probability). Several other CoCoRaHS sites in the Cave Spring area or Roanoke County had comparable amounts of rainfall, with amounts over 11 inches. A significant debris flow was reported near Poages Mill that covered both lanes on Sunnycrest Road and brought down a number of trees and a couple of utility poles. VDOT reported substantial damage to road infrastructure in Roanoke County.

The COOP station at Bedford 4 NW (BDFV2) had 5.67 inches of rain in the 4-day period ending 700 AM EST on the 22nd. This was the 4th highest 4-day total for the month of May with broken records back to 1893. The existing 4-day records are all from the month of May 2018.

The NWS Cooperative station at Roanoke 8 N (ROAV2) had its wettest May day on record with 3.41 inches for the 24-hour period ending 700 AM EST on May 21st. The previous May record was 2.40 inches set the day before, May 20, 2020. Records for 3-day rainfall, at 7.99 inches and 4-day rainfall at 9.62 inches, both ending 700 AM on May 22nd were also established at this site. For a 4-day period this rainfall total is in the 90 percent confidence interval (8.81 to 10.50 inches) for a 100-year recurrence (.01 annual exceedance probability). Complete data extends only back to 1998 at this site. Among other impacts, the persistent rainfall caused the nearby Carvins Cove Reservoir to overtop the emergency spillway for only the 2nd time since 1928 and the first time since the flood of November, 1985.

The NWS Cooperative station at Woolwine 4 S (WLWV2) had its wettest May day on record with 5.52 inches for the 24-hour period ending 700 AM EST on May 21st. The previous May record was 3.61 inches on May 12, 1961. An all-time record for 3-day rainfall at 10.25 inches ending 700 AM on May 22nd was also established at this site. For a 3-day period this rainfall total is in the 90 percent confidence interval (9.57 to 11.50 inches) for a 50-year recurrence event (.02 annual exceedance probability). At a 4-day duration this station measured 11.90 inches, the 2nd highest of any 4-day period on record (after September 27-30, 2015 at 13.34 inches). For a 4-day period this rainfall total is in the 90 percent confidence interval (11.4 to 13.7 inches) for a 100-year recurrence event (.01 annual exceedance probability). Complete data extends back to 1952 at this site. Considerable damage occurred to roads and transportation infrastructure in Patrick County according to VDOT.

The NWS Cooperative station at Martinsville (MARV2) had its 3rd wettest May day on record with 3.10 inches for the 24-hour period ending 700 AM EST on May 21st. The existing May record is 3.85 inches on May 19, 2018. A May record for 2-day rainfall was set with 4.95 inches ending 700 AM on May 21st and a 3-day record of 6.63 inches ending 700 AM on the 22nd. The 4-day record for May was also established at 7.73 inches. Nearly complete data extends back to 1931 at this site.

The COOP station at New Castle (NWCV2) had a 2-day rainfall total of 4.77 inches ending at 700 AM EST on the 22nd which was a record for the month of May and 9th highest for any 2-day period. For the 3-day period ending the same day, the station recorded 6.12 inches, the highest ever for May and 4th highest for any 3-day period. The 3-day total was in 90 confidence interval (5.65-6.63 inches) for a 25-year rainfall event (.04 annual chance of occurrence). Extensive road damage was reported by VDOT in the County.

The COOP site at Pearisburg 4 SSE (STFV2) measured 4.15 inches in the 3-day period ending at 700 AM on May 22nd. This was the 2nd highest 3-day total in May with records back to 1952.

Wise Avenue was closed due to overflow from Tinker Creek. This is a low-water bridge that is inundated below flood stage on the creek. The gage height on the USGS Tinker Creek above Glade Creek gage was around 7 feet at the time of this report. The stream crested at 14.77 feet on the afternoon of the 21st.

The Roanoke River at Glenvar (GNVV2) crested at 14.14 feet (13400 cfs) in the early afternoon of the 21st. Flood stage is 9 feet. It was the 9th highest stage on record but data only extends back to 1992 at this gage. Several roads were closed near the river including Southwest River Road. Bohon Hollow Road bridge (Route 734) about 1 mile upstream from gage was overtopped. According to USGS statistics it was near a 5-year flood event (0.2 annual chance of occurrence).

Tinker Creek was reported to be flooding portions of 13th Street from Eastgate Avenue to Mason Mill Road. The gage height on the USGS Tinker Creek Upper near Columbia gage was around 9 feet at the time of this report. The stream crested twice during the event, at 12.58 feet late on the 20th and 13.49 on the afternoon of the 21st. Per USGS data, the peak discharge of 3920 cfs was slightly below a 5-year flood event (0.20 annual chance of occurrence) on upper Tinker Creek.

Several low water bridges along Goose Creek were reported to be flooded and Goose Creek Run Road was flooded.

The persistent heavy rains produced a substantial landslide in Salem in the 2400 block of Franklin Street. An eyewitness in a media report described it, 'all of a sudden the land just started moving. The whole point of the mountain started sliding down, trees falling everywhere.' A nearby CoCoRaHS site in Salem (VA-RN-21) measured 10.70 inches in the 4-day period ending 700 AM on May 22.

A spotter reported water several inches deep on Bennington Street from the Roanoke River around 850 PM EST on May 20th. The stage at the time of the report was around 13 feet on the Roanoke River gage at Walnut Street (RONV2). Several hour later the footbridge to the Carilion Hopsital was overrun and inaccessible. Several roads around the hospital were under varying amounts of water, up to a depth of a few feet. The reading on the Roanoke River gage was around 15.7 feet at the time of this report. The river crested at 15.89 feet at 310 PM EST on the 21st. Moderate flood stage is currently 12 feet and Major flood stage is 16 feet. This was the 8th highest stage on record at this gage, with records back to 1899. According to USGS statistics it was slightly under a 10-year event (0.1 annual chance of occurrence). Social media images also showed floodwaters from the Roanoke River covering several feet of the parking lot of the Ramada Inn and water entering the hotel, although this may have been backup along Ore Branch.

The Mill Lane low water bridge in Salem was entirely underwater and portions of W. Riverside Drive was flooded and closed along with several other roads in Salem. The nearby Salem Pump Station IFLOWS gage (SPSV2) crested at around 9.1 feet. Minor flood stage is 7 feet.

The Craig Creek at Abbott (ABBV2) IFLOWS gage crested at 10.6 feet around midday on May 21st. This was the 3rd highest crest in the fairly short (since around 2010) and erratic history at this gage site. Some roads were flooded and partially damaged Craig County according to VDOT information.

The New River at Allisonia (ALSV2) flooded with a crest of 14.16 feet (49,800 cfs) in the late afternoon of May 21st. This was the 6th highest crest on record. Moderate flood stage is 13 feet. Stage and discharge records are available back to 1930 for this gage. According to USGS data it was roughly a 10-year flood event (0.1 annual chance of occurrence).

The Roanoke (Staunton) River at Altavista (ALTV2) reached flood stage early on the 21st and crested at 23.59 feet (31,000 cfs) early on the 22nd. This was the highest stage/discharge at this gage since September, 1996 with the remains of Hurricane Fran.

Local news reports said many roads were flooded and damaged across Franklin County. Several were closed due to large mudslides, including Five Mile Mountain Road in southern Franklin near the Floyd County line. A section of Virginia 116 (Jubal Early Highway) in the Coopers Cove area was as the road collapsed in the early morning hours on May 22 during prolonged rainfall, according to VDOT officials. VDOT estimated that repairs would take approximately one to two months before the road can reopen to traffic. Dozens of other roads were closed at various times due to flooding.

Media reports showed water overtopping a portion of Spring Valley Dam in Roanoke leading to the evacuation of 13 homes due to the potential risk of a dam failure.

The Dan River at South Boston (SBNV2) exceeded Moderate flood stage of 29 feet, cresting at 30.11 feet on the morning of May 24th. This was the 12th highest stage at this gaging site since records began in 1924, although there are breaks in the period of record. Flood stage categories on the Dan River were adjusted upward by several feet in May 2019. The peak discharge from this flood of 45,400 cfs was estimated to be between ad 5- and 10-year flood event (0.2 to 0.04 annual exceedance probability) according to USGS studies. Several roads around South Boston were flooded and businesses in the Riverdale area flooded.

The New River at Galax (GAXV2) flooded with a crest of 11.75 feet (47,600 cfs) on the afternoon of May 21st. This was the 8th highest crest on record and the highest discharge since January, 1995 (a higher stage occurred in January 2010 due to an ice jam). Stage and discharge records are available back to 1934 for this gage. According to USGS data it was roughly a 10-year flood event (0.1 annual chance of occurrence). Several roads were flooded and there was some road damage. Images on social media showed the New River well out of banks and flooding some campgrounds and equipment near Pleasant Grove Road.

The New River at Radford (RDFV2) flooded with a crest of 21.71 feet (93,500 cfs) near midnight on May 22nd. This was the 6th highest crest on record. Major flood stage is 20 feet and Moderate flood stage is 16 feet. Stage and discharge records are available back to 1896 for this gage. According to USGS data it was roughly a 10-year flood event (0.1 annual chance of occurrence).

The intersection of Craig Creek Road and Roaring Run Road was closed due to high water. The gage on Craig Creek at Parr (CRGV2) was around 13.3 feet at the time of the report. Minor flood stage is 12 feet. The stream crested at a stage of 16.20 feet (16200 cfs), the highest level since September 2004 (19.87 feet) when the remains of Hurricane Jeanne plowed through the area. It was the 7th highest on record at the gage since 1925 and was slightly below a 10-year flood event (0.1 annual chance of occurrence). Moderate flood stage is 15 feet and several roads were flooded.

Walker Creek was reported to be flooding and blocking Flat Hollow Road with water several feet deep. The Walker Creek gage at Bane (BANV2) was at a stage of around 11.4 feet at the time of the report and Minor flood stage is 11 feet. The gage crested at 14.19 feet in the morning of the 21st. Rye Hollow Road was also flooded and closed. According to USGS data the peak discharge of 13500 cfs was roughly a 5-year flood event (0.2 annual chance of occurrence).

Tinker Mill Road was flooded and Tinker Creek reported out of its banks.

Lone Ivy Road was reported to be flooded. The Smith River near Woolwine gage (SMWV2) rose above Minor flood stage of 9 feet by 545 AM EST and crested at 9.75 feet at 845 AM EST. This was the 5th highest stage in the period of record at this gage with data back to 1995. According to USGS data this was just below a 10-year recurrence interval flood (0.1 annual chance of occurrence).

Catawba Creek Road was reported to be flooded with water of unknown depth. The USGS gage on Catawba Creek near Catawba (CTWV2) crested at 7.87 feet (3660 cfs)|early on the 21st. This was the 8th highest stage on record at this gage with data back to 1954. Only Hurricane Michael in October 2018 has had a higher stage (7.98 feet) in the past 15 years, dating back to September 2004. According to USGS data this was close to a 5-year recurrence interval flood (0.2 annual chance of occurrence).

The New River at Ivanhoe (IVNV2) flooded with a crest of 20.77 feet (49,800 cfs) in the late afternoon of May 21st. This was the 4th highest crest on record and the highest stage/discharge since Novermber, 1977 when the river level reached 28.08 feet. Stage and discharge records are available back to 1931 for this gage. According to USGS data it was roughly a 10-year flood event (0.1 annual chance of occurrence).

The Dan River at Danville (DVLV2) exceeded Moderate flood stage of 26 feet, cresting at 27.57 feet early on the morning of May 23rd. This was the 3rd highest stage at the current gaging site after the remains of Hurricane Fran in September 1996 (28.65 ft.) and Hurricane Michael in October, 2018 (30.01 ft.). Flood stage categories on the Dan River were adjusted upward by several feet in May 2019. The peak discharge from this flood of 43,900 cfs was estimated to be slightly in excess of a 10-year flood event (0.10 annual exceedance probability) according to USGS studies. Several roads were closed by flooding in the Danville area.

Flooding was reported along portions of the Little River in Floyd County. Water was reported covering a portion of Thunderstruck Road due to flooding from the Little River and further downstream, Sowers Mill Dam Road was flooded. No gage is available in Floyd County, but the Little River crested a little below Minor flood stage downstream on the gage near Graysontown (GRYV2).

The New River was flooding and over the top of the Dixon Ferry (Route 606) bridge on near Fries. Social media images showed the water several feet deep with debris mixed in. Some camping equipment along the river was also flooded. The upstream gage on the New River near Galax (GAXV2) was at a stage of around 9.6 feet at the time of this report and Minor flood stage is 9 feet.

The New River was out of its banks and blocking Big Falls Road near the Giles County line with up to 1 foot of water. Both the upstream gage on the New at Radford and downstream at Glen Lyn crested above the Major flood category.

Multiple Creeks in the Buffalo Ridge area were out of their banks and numerous roadways blocked by floodwaters. The spotter reported 11.33 inches of rain in the event so far. VDOT reported considerable road and infrastructure damage in Patrick County.

News reports showed Toms Creek flowing across the Route 654 (Brooksfield Road) one-lane bridge and flooding all the nearby lowlands. The road was closed.

Stroubles Creek flooded across Plantation Road.

The New River at Glen Lyn (GLLV2) flooded with a crest of 18.93 feet (115,000 cfs) very early on May 22nd. This was the 5th highest crest on record. Major flood stage is 18 feet and Moderate flood stage is 16 feet. Stage and discharge records are available back to 1915 for this gage. According to USGS data it was not quite a 25-year flood event (0.04 annual chance of occurrence). Lurich Road was flooded and closed according to reports.

The New River at Glen Lyn (GLLV2) crested at 18.24 feet, just above the Major flood stage of 18 feet very early in the morning of May 22nd. This was the highest stage since the remains of Hurricane Michael in October 2018 and the 5th highest on record since 1940. The peak discharge of 115,000 cfs was somewhat less than a 25-year recurrence interval (0.04 annual chance flood) according to USGS data. Several roads near the river were flooded and closed.

A vehicle was trapped in flooding from the New River along Hazel Hollow Road and a water rescue was conducted. The New River at Radford just downstream was flooding during this period and crested just above Major flood stage.

The Dan River at Paces (PCEV2) exceeded Moderate flood stage of 29 feet, cresting at 29.13 feet on the afternoon of May 23rd. This was the 9th highest stage at this gaging site since continuous records began in 1951 and including the August 1940 flood. Flood stage categories on the Dan River were adjusted upward by several feet in May 2019. The peak discharge from this flood of 48,700 cfs was estimated to be near the 25-year flood event (0.04 annual exceedance probability) according to USGS studies. Route 658 was flooded and closed by the river.

Several news outlets reported the closure of heavily traveled Route 460 due to road damage and a large mudslide. The mudslide occurred about five miles east of the West Virginia line. VDOT provided road repair estimates.