MARKHAM FERRY
OperatingHydro power plant
- Capacity
- 124 MW
- Primary fuel
- Hydro
- County
- Mayes County
- Operator
- GRAND RIVER DAM AUTHORITY
- Status
- Operating
- Commissioned
- 1964
- EIA plant ID
- 2980
- Coordinates
- 36.2301, -95.1823
MARKHAM FERRY, a 124 MW Hydro power plant in Mayes County, Oklahoma. Operated by GRAND RIVER DAM AUTHORITY, commissioned 1964.
Weather peril exposure
MARKHAM FERRY is a 124 MW hydro power plant in Mayes County, OK, operated by GRAND RIVER DAM AUTHORITY, commissioned in 1964. Mayes County carries high modeled catastrophe exposure in the FEMA National Risk Index, scoring 3.6 of 5 at the 64th national percentile. Ice storm is the leading peril, rated Very High by FEMA at the 99th percentile.
The Bywatts loss layer is calibrated to solar PV hardware, so it is not applied to a hydro plant. The ratings below are the FEMA National Risk Index county hazard ratings for this location.
Mayes County hazard ratings
| Peril | FEMA rating | National percentile | Peril score | Events per year |
|---|---|---|---|---|
| Ice storm | Very High | 99th | 4.9 of 5 | 1.4 |
| Riverine flooding | Relatively Moderate | 83rd | 4.3 of 5 | 1.7 |
| Winter weather | Relatively Moderate | 83rd | 4.3 of 5 | 9.3 |
| Wildfire | Relatively Low | 81st | 4.2 of 5 | <0.01 |
| Heat wave | Relatively Moderate | 79th | 4.2 of 5 | 23.3 |
| Lightning | Relatively High | 76th | 4.0 of 5 | 55.5 |
| Hail | Relatively Low | 63rd | 3.5 of 5 | 9.2 |
| Strong wind | Relatively High | 61st | 3.5 of 5 | 7.5 |
| Earthquake | Very Low | 54th | 3.2 of 5 | <0.01 |
| Tornado | Relatively Moderate | 34th | 2.3 of 5 | 0.76 |
| Hurricane | Very Low | 31st | 2.3 of 5 | <0.01 |
Perils not assessed in Mayes County
These perils carry no usable National Risk Index figure for this county, so they are excluded from the scoring rather than scored zero. A zero would claim the peril was assessed and found benign.
| Peril | Why it is not scored |
|---|---|
| Coastal flooding | FEMA rating is "Not Applicable" for this county |
Model hail, wind and flood exposure for Mayes County in the weather risk calculator
Ratings are the FEMA National Risk Index county hazard ratings; the peril score is a Bywatts transform of the FEMA national percentile. Full data sources and the solar vulnerability methodology are in the weather risk calculator.
Modeled estimate for screening and negotiation. Built from FEMA National Risk Index county hazard data and a solar vulnerability layer documented above. Not a quote, a binder, or actuarial advice, and not a substitute for a carrier's own model. Hazard data: FEMA National Risk Index December 2025, synced 2026-07-24. Resolution is county level, not site level.