Lidar helps geologists and others spot potential hazards such as areas at risk of landslides, but also provides unseen details of our fishing and hunting grounds.
By Andy Walgamott
Trib 87 was troublesome.
The tiny stream that feeds the Sammamish Slough vexed the city of Woodinville during the years I covered my hometown for the local weekly newspaper.
If memory serves, the city council and business folks had visions of developing the area where the creek spilled off tony Hollywood Hill and met the valley near Chateau Ste. Michelle and the Redhook Brewery, but where the flood-prone tributary should be tucked away out of sight and out of mind was problematic.
When it was put into a concrete raceway along 148th just north of the old schoolhouse, someone promptly stuck their car in it. When it was dewatered, a handful of dead fingerlings unexpectedly turned up in a low spot.
Even though I’ve forgotten much from those cub reporting days, I distinctly remember an exasperated council member turning to me and asking where I thought Trib 87’s historic channel was located.
I could see it plain as day: everywhere within a quarter mile of where it poured off the hillside onto the valley floor.
That’s where Trib 87 (now known as Derby Creek) acted as an alluvial fan. The rise of the land towards that point told me that since the Great Berg melted back to Canada, rain, snow and gravity had been doing their best to flush the hillside across what would eventually become the city’s tourist district.
A TRAINED GEOMORPHOLOGIST I’m not, I will admit, but I do have more than a passing interest in Northwest landscapes.
I’ve spent several decades exploring them, fishing them, hunting them, photographing them, reading about them, wondering about them, poring over maps of them.
Speaking of maps, give me one and I am taken away. Doesn’t matter where it is, what it shows, what language it’s in, they suck me in. One of my wife Amy’s recipes is written on the back of a map of somewhere in the country she was born in, Germany. The 4-inch by 4-inch snippet shows some dorf and surrounding landschaft in exquisite detail – I could stare at it until the oven timer beeps and not get bored.
So as you can imagine I was enthralled this winter when the Washington Department of Natural Resources posted Lidar imagery for large swathes of Washington.
Lidar stands for light detection and ranging, and without going into all the techy stuff about how it all works, it’s basically X-ray vision. People flying around in airplanes use lasers and computers to see through the Earth’s clothes, which is to say the trees, shrubs and whatnot it’s swaddled in, producing a map that shows the true land of the land.
It really shines in well-watered Western Washington. Where on the Eastside, topographic features such as the Missoula Floods’ giant ripple marks on the Wenatchee area’s Crescent Bar stand out because the sagebrush only grows so high, vegetation hides all on the Westside.
FOR A WEEK right after DNR’s early January launch of the site (lidarportal.dnr.wa.gov), after our boys were in bed I spent my evening free time zooming around my favorite spots covered by the data, moaning in exaggerated delight (to Amy’s increasing disgust) at what the subtle silver shading showed me.
Ancient river terraces, entrenched meanders, gigantic Ice Age channels, abandoned runoff deltas facing into the Cascades, fluted drumlin fields, mysterious mounds, wavecut beaches high above Puget Sound, the zigzag of logging roads up steep mountainsides, fault lines, scarps and landslides, and more hidden features were all suddenly visible.
One of the most interesting things I found was a series of pinpricks near Mount Rainier, revealed as if the Earth could no longer keep a little heroin habit secret. Eventually I realized they were likely artifacts of old coal mines near Carbonado.
Well to the north, in the forests of Larrabee State Park were anticlines and synclines worthy of the Appalachians, and cupping narrow lakes that Doug Huddle wrote about fishing in his North Sound column last May.
In central Snohomish County, bass- and trout-rich Flowing, Panther and Storm Lakes sit among a field of long, low, cone-shaped hills that mark where the glacier bent towards the southeast to fill up the Skykomish Valley clear back to just east of Reiter Ponds.
Speaking of the Sky, down at its lower end a series of oxbows amongst the cow pastures of the Tualco Valley make me wonder if that river and not the much closer Snoqualmie was responsible for digging out what is today Crescent Lake.
The vast flats between Tacoma, the town of Rainier and Olympia are revealed to be a complex mix of supersized channels that sent Pugetropolis runoff through Grays Harbor, and rumpily-frumpily ground where great bergs were surrounded by runoff and filled to become Lake St. Clair and other kettles we fish today.
Ahh, I literally could go on forever, but let me wrap up in Darrington, deep in the Cascades. I was out there on the last weekend in January that the Sauk was open for fishing and had hooked a couple bull trout and was trying for something shinier. But I couldn’t help casting back in my mind to the Lidar maps I’d seen of where the river once turned left down the valley of the North Fork Stilly but now plows north in a great side to side milling of boulders, gravel, sand and glacial grit, speaking to deep time and earth processes that are mostly obscured from view, save for the subtle bar I walked up to a hole I hoped hid a steelhead.
While Lidar is meant for scientists, engineers, planners and others (for more see dnr.wa.gov/lidar), it also lets us see the true land of this land we fish and hunt, revealing its secrets and ever deeper mysteries.
What’s up with those thin lines across the western shoulder of Mt. Haystack above the Sky?