Why does Tulsa's flood history matter for Oklahoma foundations?
In short: Tulsa has a long record of creek and river floods, peaking with the 1984 Memorial Day flood on Mingo Creek. Those floods led to buyouts, floodplain rules in 1977 and a stormwater fee in 1986. For foundations, creek corridors matter because they hold deep, soft deposits and water close to the surface, unlike nearby upland ground on shale.
What were Tulsa's major floods?
The City of Tulsa's flooding history lists these events 1:
| Date | Water body | What happened |
|---|---|---|
| 1908 | Arkansas River | Flood a year after statehood 1 |
| June 13, 1923 | Arkansas River | Waterworks flooded; 4,000 left homeless 1 |
| 1943 | Arkansas River | Led to Corps of Engineers levees around refineries 1 |
| Mother's Day 1970 | Mingo and Joe creeks | Creek flooding 1 |
| Labor Day and Dec. 1971 | Flat Rock, Bird and Haikey creeks | Bird Creek flooded twice 1 |
| 1974 | Bird, Joe, Fry, Haikey and Mingo creeks | Mingo Creek flooded in June and again in September; some residents had their third flood in a year 1 |
| Memorial Day 1976 | Mingo, Joe and Haikey creek headwaters | About 10 inches in 3 hours; 3 deaths; over 3,000 buildings damaged 1 |
| Memorial Day 1984 | Mingo Creek mainly | About 15 inches overnight; 14 killed, 288 injured; nearly 7,000 buildings damaged or destroyed 1 |
| 1986 | Arkansas River | Keystone Reservoir releases of 310,000 cubic feet per second; 64 buildings damaged 1 |
The city describes the 1984 flood as the worst in its history 1.
What changed after the floods?
- 1971: Tulsa adopted a 100-year flood standard 1. A 100-year flood has a 1% chance of happening in any year.
- 1974: 33 houses were cleared from the Mingo Creek right-of-way 1.
- 1977: comprehensive floodplain regulations adopted 1.
- 1984: 300 flooded homes relocated, plus a 228-pad mobile home park 1.
- 1986: a stormwater utility fee created by ordinance, and 13 substantially damaged structures cleared 1.
- Early 1990s: FEMA ranked Tulsa first in the nation for its floodplain management program 1.
What about flooding in Oklahoma City?
Flooding is a statewide hazard; an Oklahoma Geological Survey summary lists floods among Oklahoma's six main natural hazards 4. Heavy rain also hits central Oklahoma: in May 2015 Oklahoma City received 19.48 inches, its wettest month on record 5. For more on rain extremes, see drought and wet years.
Why do creek corridors matter for foundations?
Deep soft ground near water
Creeks and rivers lay down alluvium, loose sediment of clay, silt and sand. Along the Arkansas River in Tulsa County, shale lies about 5 to 10 feet below the river bottom but generally 20 to 30 feet below the banks 2. Borings at the Sand Springs and South Tulsa/Jenks sites found 18 to 35 feet of soil over rock along the banks 2.
On 91st St South between Memorial and Mingo, borings for one retaining wall hit weathered shale near 13.5 feet, while borings for a second wall went through clay to 30 and 35 feet without finding shale, and hit water at 13.5 to 15 feet 3. See Quaternary alluvium and terraces and soft soil consolidation.
Bank erosion and slope movement
Floodwater and fast creek flow can cut into banks and undermine nearby yards, fences and slabs. The Oklahoma Geological Survey notes that most Oklahoma landslides occur in the eastern third of the state, where wetter climate and steeper terrain raise the risk 4. Related pages:
Piers near creeks
Because depth to rock can change sharply over short distances near water, from about 5 to 10 feet under the Arkansas River bottom to 20 to 30 feet under its banks 2, and from about 13.5 feet at one 91st Street wall to deeper than 35 feet at the other 3, foundation piers on creek-side lots may need to go deeper or stop on friction in soil rather than on rock. Boring comparisons are in borings: depth to rock in Tulsa and OKC.
Related
- Erosion, creeks and slopes
- Groundwater and perched water
- Depth to rock from borings
- Slope and erosion stabilization
- Tulsa metro region
Common questions
What was the worst flood in Tulsa history?
The Memorial Day flood of 1984, when about 15 inches of rain fell overnight. It killed 14 people, injured 288 and damaged or destroyed nearly 7,000 buildings, mostly along Mingo Creek.
Which Tulsa creeks have flooded most often?
City records list repeated floods on Mingo, Joe, Haikey, Fry, Bird and Flat Rock creeks, with Mingo Creek flooding at least twice in 1974; for some residents that was a third flood in a year.
When did Tulsa adopt floodplain regulations?
Tulsa adopted a 100-year flood standard in 1971 and comprehensive floodplain regulations in 1977. A stormwater utility fee was created by ordinance in 1986.
Is the soil different near creeks?
Often, yes. Along the Arkansas River in Tulsa County, shale is about 5 to 10 feet below the river bottom but generally 20 to 30 feet below the banks, with soil and river deposits filling the space above.
Sources
- Flooding History City of Tulsa
- Arkansas River Corridor Projects: Existing Geotechnical Resource Review Tulsa County River Projects
- Geotechnical Engineering Report, Retaining Walls A and B Along 91st Street South from South Memorial Drive to South Mingo Road City of Tulsa
- Abstract: Geologic Hazards in Oklahoma Geological Society of America (Oklahoma Geological Survey author)
- Oklahoma Monthly Climate Summary, May 2015 Oklahoma Climatological Survey
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