Giant Current Ripples at Omak, WA

Focus Shifts North

Paleo-outburst flood indicators including large bedform trains and iceberg scour marks have been discovered in Okanogan Valley and other south-trending valleys of NE Washington (Gombiner & Lesemann 2024, Lesemann et al. 2024). Identical features are known in the Channeled Scabland and other outburst flood tracts worldwide, including Iceland. The features document glacial floods of significant size and sourced in southern British Columbia spilled south into Washington State, inundating glacial Lake Columbia and the Columbia River gorge. Large bars near Wenatchee WA preserve a partial record of their passing. Discharge is estimated at 104-105 m3s-1, and possibly as high as 106 m3s-1. Absolute age of the deposits is not known, but field relationships indicate they post-date the MSH Set S tephra and roughly coincide with the last drainage of glacial Lake Missoula. The discoveries confirm large-volume glacial outburst floods occurred well north of the long-established floodway margin and highlight the need for an expanded view of flood hydrology in areas north of the ice sheet terminus.

The Okanogan Valley has for decades been considered to have played no significant role in Ice Age flooding of the Channeled Scablands. Montana water, not Canadian water, is believed responsible for carving the Scablands. That view might be changing.

Omak lidar image. Giant current ripples (large gravel dunes) atop a glacial terrace near Omak, WA. Omak is located along the Okanogan River, which flows south out of British Columbia and empties to the Columbia River at Brewster, WA. The ripples ornament a broad outwash flat that stands as the second-highest Pleistocene-age terrace in this portion of the valley. The ripple train is truncated on its east side. It may have once extended much farther out into the valley. Young alluvial fans spill east from the shadowed gullies. The south end of the ripple field is muted, partially buried by sand dunes and loess. Omak River Rd intersects Hwy 97 and descends the escarpment near the center of the image. The Okanogan River is at right.

I discovered these giant current ripples in 2019 and emailed this image out to several geologists. I showed them to Jerome Lesemann in July 2020 via email, to Jim O'Connor in June 2021 in Upper Grand Coulee, and to Richard Waitt in May 2022 during breakfast at a Walla Walla Starbucks. The Omak ripples are cool enough to have made it into a 2024 PBS Digital Studios video called 'Earth's History is Hidden in These Strange Maps' featuring Dan Coe and Dr. Joel Gombiner.

The unusual bedforms are of similar scale to features found at several classic localities in the Channeled Scablands. Bretz (1969, Fig. 1) shows 14 GCR locations in southeastern Washington. Baker (1973, Plate 1; Appendix II) mapped 60 locations and suspected, "A detailed survey of the aerial photography over scabland channels would probably reveal well over 100 trains of giant current ripples in various states of preservation". His field- and aerial photo-based analysis determined ripple wavelengths that required flow depths 40-500 feet deep and velocities 30-60 ft/sec. The giant ripples (GCR) at Omak are Late Pleistocene in age and were produced by a sizeable flood down the Okanogan Valley, but one likely sourced locally and smaller than most Missoula floods.

The importance of giant current ripples in Okanogan Valley is that they indicate the valley contributed some amount of water to the Scabland region. Some portion of constructional bars and other flood features along the mainstem Columbia Valley south of Brewster can be attributed to water that did not originate from Glacial Lake Missoula.

Baker's GCR sites. Vic Baker's list of GCR sites he identified in aerial photos (Baker, 1973).

Bretz's early mapping. Thirteen giant current ripple locations identified by Bretz (1969, Fig. 1). Bretz began noting giant ripples in the 1920s. According to notes from his 1924 field season, "A closer scrutiny of the Devil's Canyon bar shows portions of a larger older feature on which the [bar] described has been built. The topographer who sketched this was quite at sea as to its origin. He shows it as a minor ridge projecting from the west wall, due to post-canyon dissection by local drainage." A hand written note in the margin reads, "But I didn't recognize the giant ripples for what they are."

Lidar image footprint. Giant current ripples at Pogue Flat north of Omak, WA. Photo is same scale as the West Bar image.

Lidar image overlay. Giant current ripples at Pogue Flat in the Okanogan Valley are smaller and lower-relief than those at West Bar in the Columbia Valley. The flood that created them was certainly less voluminous than any of the Missoula floods, but it was still pretty large. The following images all have the same scale bar.

The source of the water that produced the GCR field at Omak is not currently known. It came from somewhere to the north. Potential sources for the water are near and far. Perhaps an outburst flood was released from behind an ice-dammed lake in a nearby tributary valley such as Pine Creek near Tonasket. Catastrophic releases from a subglacial reservoir is also possible (i.e., Lesemann and Brenand, 2009). Perhaps a long-traveled flood from far-retreated ice in Canada made its way south through a system of bedrock channels (Loomis-Palmer Lake-Sinlahekin-Similkameen) and into the main valley trough near Omak. My eye sees subaerial overland flooding in the Omak ripples.

Johnson Creek Fan. Crosscutting relationships indicate four steps in the evolution of Pogue Flat and the nearby portion of the Okanogan Valley. Ripple field occurs at an acceleration point, as floodwater moved off the bench into the valley (green to blue transition). I made this map and others in this post.

Time 1.) Deposition of Johnson Creek Fan (boulder gravels) by energetic east-directed flows into an existing (partially excavated) Okanogan Valley. A prominent radial network of small-scale channels is clearly visible on aerial photos and in the field on Bid-A-Wee flat and near the Omak Airport.

Time 2.) A younger, smaller outburst flood (or possibly just vigorous outwash channels) sourced from the same basin near Conconully (Fish Lake Reservoir) incised the coarse grained fan deposits. If a flood, then the lake filled and spilled twice. Landforms suggest flow was not long lived and bifurcated abruptly at The Prow, spilling both north to Riverside and south to Omak. These routes indicate Pogue Flat was essentially as flat as it is today (no isostatic uplift signal) and flows drained to the floor of Okanogan Valley, which was at an elevation lower than Pogue Flat.

Time 3.) Energetic south-directed flow along the main Okanogan Valley truncates the Johnson Creek Fan surface and locally forms giant current ripples (GCR) on a slighly lower tread. GCR appear to have moved down the trunk valley rather than from tributary Johnson Creek. The Okanogan Valley at Time 3 was not as deeply incised as it is today; it was either mostly filled with outwash and glaciolacustrine sediment or plugged with ice.

Time 4.) Continued excavation of an ice-free Okanogan Valley by outwash and tributary streams.

HRTM. The giant ripples at Omak show up well on this lidar point cloud-derived HRTM image created and sent to me by Michael Davias. His color ramp uses 20x vertical exaggeration. Davias' imagery may be an efficient way to prospect for other GCRs and find use in surficial geologic mapping in general. Very cool. Check out his work at cintos.org.

West Bar, WA. Giant current ripples at West Bar, WA. Scale bar shown.

Markle Pass, MT. Giant current ripples in the Glacial Lake Missoula Basin of western Montana (Pardee, 1942). Water flowed north out of Little Bitterroot Valley over Markle Pass and into Camas Prairie.

Odessa, WA. Giant current ripples in Crab Creek Coulee along Hwy 28 just west of Odessa, WA. According to Waitt (2009, Stop1.7b), the ripples are spaced 166 ft (50 m) apart and ornament an "upland crescent bar" that merges with scabland.

Wilson Creek, WA. Giant current ripples in upper Crab Creek Coulee east of Wilson Creek, WA. See Bretz (1956, 1959), Baker (1973, 1978), and Waitt (2009, Stop 1.8a) for discussion.

Conconully area, WA. Four or more terrace levels at Fish Lake near Conconully, WA. Some composed of till. Matsura photo (#6578). Okanogan County Historical Society archives.

Landforms consistent with local outburst floods spilling from a side canyons into the main Okanogan Valley were noted by early geologists (Russell, 1893, 1898; Dawson, 1898; Waters, 1933), but none mentions giant current ripples. Flint (1935) came close with his "undulatory topography", but lacking a hot air balloon appears not to have found the ripples at Omak,

The upper surface of this terrace is marked by meander scarps and meander channels, some of them broad and deep, by extensive fans apexing at tributary mouths, by groups of kettles individually reaching half a mile in length, and locally by undulatory topography with closed depressions, suggesting irregular letting-down of sediment over deeply buried, wasting ice.

Pogue Flat c.1909. Glacially-sculpted hills north of Omak (Three Buttes) with the higher Limebelt hills beyond. Matsura photo (#7735). Okanogan County Historical Society archives.

If you ask me, the giant ripples at Omak appear related to a flood spilled from nearby Johnson Creek Valley that heads near Conconully (Fish Lake). Johnson Creek enters the Okanogan Valley from the west just north of Omak, WA. Energetic overland flows formed "The Prow" east of the Omak Airport (Johnson Creek Rd and Blue Heron Ln) and covered Sand Flat-Pogue Flat in boulders (Omak Airport area). I lived in Omak for 5 years, right next to the airport, commuting 55 miles over Disautel Pass to Nespelem for work each day. Wore out two Subarus.

The Okanogan Valley contains an extensive kame and outwash terrace system. Flights of terraces composed of sand and gravel line the entire valley from Osoyoos to Brewster. Some are pocked with kettles, others are scoured by ancient streams. Sediments in the terraces are the preserved record of glacial ice of the Okanogan Lobe retreating north at the end of the last Ice Age. Enormous volumes of water flowed along the margins of stagnant(?) and downwasting ice, transporting sediment downvalley toward the Columbia River. A group of local geologists - bright, observant, amateurs - used to tell me that there's a lot more lake sediment stored in the Okanogan Valley than people think. Those gentlemen also spoke of boulder-sized erratics perched on hillsides far above the valley floor. The terrace and incision history, the architecture of ice-marginal deposits, and the contours of ice marginal lakes remain a frontier for discovery.

The talented geology Professor Jerome Lesemann of Vancouver Island University is now working in the Okanogan and beginning to sort things out. I hope to soon meet up with him in the field. Nick Zentner recently did some filming with Dr. Lesemann near Omak. Scroll all the way down to check out their YouTube video.

The geological community has resisted the idea of large glacial floods coming down the Okanogan Valley (and other northern valleys). The current consensus is neither the Okanogan nor the Sanpoil contributed anything more than tickles of meltwater. Certainly not megafloods that scoured the Channeled Scablands. And they have a point: A satisfactory hydrologic connection between northern valleys and southern scablands has not been made. However, few flood geologists alive today have spent a significant amount of time examining the Okanogan Valley's glacial geology. And there's some scars from battles waged decades ago that still show.

Field evidence in the valley, Omak's giant current ripples being one example, seems to hint at a new chapter in megaflood research. Flint and colleagues got a lot right up here. But they didn't stay long enough to nail down the details and some of their interpretations show it.

I'll shut up after this. J Harlan Bretz's triumph over the East Coast naysayers came down to boot leather field work and first-hand observations. Not fancy models, not sophisticated theories, not elegant deduction. The doubters who found his evidence so easy to dismiss from their office chairs, were left dumbstruck at the Dry Falls rim. While the Okanogan Valley will never be the Channeled Scablands and there is no modern day J Harlan Bretz, the valley is there. The evidence is there. People just need to go look and see if there's something to discover, then sort it out. The Canadians just might have something to teach us.

Johnson Creek and Pogue Flat. Pogue Flat-Sand Flat area north of Omak, WA. The arcuate swales ("scour channels"), seen near the airport, are 1-3m deep and form a broad fan pattern.

Johnson Creek mouth. Zooming in on a Pleistocene-age landform called "The Prow". The feature is several meters high, composed of coarse gravel and boulders, and was clearly formed by rushing water moving east out of the Johnson Creek Valley toward the Okanogan Valley. Surface patterns indicate the larger terrace flat existed prior to being modified by this late outburst flood. Numerous relatively small lakes formed in side canyons all along the Okanogan Valley during times when ice occupied the valley and during ice retreat. Some lakes appear to have remained trapped behind glacial sediments after most of the valley ice had cleared out, eventually spilling like this one, sourced near Conconully, did.

Pine Creek Valley discovery. Energetic, south- and east-directed flow out of the Pine Creek Valley created scour patterns orthogonal to Okanogan Valley trends. Pine Creek, a tributary to the Okanogan Valley, is located west of Hwy 97 several miles north of Johnson Creek at the north end of Aeneas Lake (Pine Ck Rd-Horse Spring Coulee Rd intersection).

Zooming in. Flutes on the floor of Pine Creek Valley have upcurrent-pointing noses and were formed by rushing water moving southeastward out of Horse Spring Coulee toward the Okanogan River. They are remnant Pleistocene features. The horseshoe-shaped features are 10s of meters in length, but with subtle topographic expression. The flutes are highlighted by soil moisture and vegetation differences. Ranch buildings and gravel driveways for scale.

Ownership map for Pine Creek. Will check in with Mel Schertenleib next time I'm in town.

South-directed flow. More fluted forms in glacial sediments along Pine Creek.

South end. Flute forms on the south end of Aeneas Lake along Windy Flat Rd and N Pine Creek Rd.

Attention Zentnerds. Professor Nick Zentner of Central Washington University meets up with Canadian geology Professor Jerome Lesemann in the Okanogan Valley to talk giant current ripples, high-level terraces, and other aspects of the area's glacial geology.

GCR of Glacial Lake Penticton. Jerome recently discovered giant current ripples on a high terrace surface in the Okanagan Valley on the Canadian side. June 2022. Jerome made this map.

GCR in the Omak Trench (Kartar Valley). Hibbert (1985, p. 106) first identified giant current ripples in the Omak Trench (aerial photos). Joel Gombiner noted these giant current ripples in lidar imagery, too, in June 2022. Hasty photo interp by me.

GCR and dunes(?) at Monse. Don Hruska found these ripples at the U.S. Electrodynamics satellite array west Monse, WA (Usei Rd). These landforms ornament a terrace surface at ~385m elevation, about 36km north and 45m higher than those at Omak. Don notes the ripple forms continue north off the image above, on the east side of the shaded rock know. The yellow area closely corresponds to a Pogue series soil (outwash sediment) mapped by NRCS Soil Survey. Interp map by me (don't blame Don).

GCR at Malaga. Found these giant current ripples south of the Malaga Alcoa Hwy near Malaga, WA (June, 2022). Malaga Fire Department with green roofs. Elevation is ~235m. Not sure if these have been reported. December 2002 photo.

GCR at East Wenatchee. Spotted these giant current ripples north of Grant Road in East Wenatchee, WA. Certainly others found these long before me. Elevation is ~405m. Charles Mason reports giant ripples on Pangborn Bar in his self-published book 'The Geological History of the Wenatchee Valley and Adjacent Vicinity' (Mason, 2006, p. 106-107). Rolling topography can be seen in roadcuts along Grant Road south of Lyle Ave as well as along 4th Street SE and 2nd Street SE. May 2015 photo.

GCR at Deep Creek. Large ripple fields west of Deep Creek community along Hwy 2 west of Airway Heights. These are well known to geologists, but not often pictured. North is to the left. Kiver and Stradling (1989) and Breckenridge (1989) show GCR in this area in guidebook articles.

Okanogan cowboy. WGS archives.

Refs

Gombiner, J., Lesemann, J-E., 2024, Okanogan Lobe tunnel channels and subglacial floods into Moses Coulee, Channeled Scablands, northwestern United States, Geology, doi.org/10.1130/G52005.1

Lesemann, J-E., Cooley, S.W., Gombiner, J., 2024, Outburst floods from the Cordilleran Ice Sheet affecting areas north of the Channeled Scabland, Geological Society of America Annual Meeting Abstracts with Programs, v. 56, Abstract 5-9