Dear Diary,
I've walked at least twice from Jackson Park to Lake City via NE 135th St, and being the grouchy sort I am, have grumbled at least twice about the hills and valleys the street crosses. These turn out to be the work of tributaries of the North Fork of Thornton Creek.
Thornton Creek and its tributaries are the most complex stream system in North Seattle. Each map I've looked at treats them so. Also, much of this system survives at least somewhat intact. So it's no wonder that the Thornton Creek watershed gets a lot of attention. The most important source for this page, in fact, is a map made by the Thornton Creek Alliance, who offer it for free download. (It's the same map as I found in Matthews Beach, photographed, and showed you in "To the Beaches!")
The land Thornton Creek drained can be summarised thus: hills in the north and east (the North Fork and its tributaries), plateaux in the south and west (the South Fork and its tributaries), with a few lowlands mostly in between. I've found this complex system difficult to write about, and have ended up with the usual breakdown - the North Fork, then the South, then the combined stream.
I've tried not to make this a boring list, but I've probably failed.
I've reserved detailed treatment of the North Fork itself for the end of this page. This page introduces three adjacent north-south oriented hills, then a sort of lowland, and a round hill; then it introduces a plateau west of all that, that's also south of most of it. The North Fork actually starts way north in Shoreline. Early in its Seattle career it curves around the southwest side of the round hill. Then it runs at the north edge of the plateau.
The North Side
We start with the hill in coastal Lake City from the last page. This hill arguably starts just north of the city limits (NE 145th St), and rises fairly quickly to a peak, 344 feet above sea level, between 39th and 40th Avenues NE and NE 135th and 137th Streets. Cedar Park is two blocks west of this peak, over 300 feet. The hill slopes very gradually south, its last 20 feet just barely north of Thornton Creek's mouth, at the equivalent of NE 91st St; the hill thus defined necessarily includes much of Matthews Beach. In the west the hill's edge can be taken as Little Brook until that stream ends at 36th Ave NE and NE 115th St. The edge then seems to shift southeast to 44th Ave NE and NE 105th St, and south-southeast beyond that.
Little Brook is a tributary of the North Fork. Pedants call it Little Brook Creek, and drive on road streets. Little Brook is shown on all topographic maps of the area that I'm using, unlike most other tributaries. The Alliance map shows it starting just south of 145th St at 27th Ave NE, and promptly heading east. It turns south at 31st Ave NE, with just enough eastwardness to reach 33rd Ave NE by NE 125th St, and then curves more to end at 36th and 115th as already mentioned. Like most surviving Thornton tributaries, it's in culverts much of its way, though usually in the open south of 125th. It passes through Little Brook Park in the open, goes past the Lake City Hub Urban Village Acquisition in a culvert, and passes through Little Brook Creek Natural Area in the open.
A short tributary runs near Little Brook, around 33rd Ave NE from NE 123rd St to the equivalent of NE 117th St, entirely in the open. I don't know whether it's a remnant of an earlier lower course for Little Brook, or what. It's on the 2020 and Alliance maps near Little Brook, and on my Rand McNally physical map without Little Brook.
The hill west of Little Brook is a small, gentle one entirely in Seattle, its 'peak' (244 feet) running along 30th Ave NE from NE 134th to 143rd Streets. It becomes indistinguishable as a hill by NE 125th St. It has Little Brook on its east, the unnamed short creek on its south, and a hypothetical streambed on its west.
The topographic lines strongly suggest a narrow valley starting not far from 28th Ave NE and NE 143rd St, running south near 28th, and ending where the North Fork crosses Lake City Way NE south of NE 120th St. No map attests this as a creek, but it could have been stopped early, because its course runs through downtown Lake City. It could well have run through Albert Davis Park, and should have drained the land where Lake City Mini-Park and Lake City Memorial Triangle now are. Virgil Flaim Park is close enough to both this and the North Fork that it could have drained to either or both.
The hill west of that is only a southern spur of a really tall hill in Shoreline's Hamlin Park. It's still 360 feet on entering Seattle, at 23rd Place NE, and doesn't entirely fade out in the south until NE 123rd St. In the west, it gets lower some by about 20th Ave NE.
The only lowland in this city-limits sequence isn't all that low; it slopes from 300 feet at those limits to 200 at the North Fork. It runs from about 20th to 15th Avenues NE. It is crossed by three streams usually in culverts.
Hamlin Creek is shown only on the Alliance map (as is typical of surviving tributaries), but topographical lines confirm that the course taken by the culverts, down 20th Ave from well into Shoreline, is close to the natural one. It's in the open, in Seattle, from just north of NE 137th to just north of 135th Streets. It reaches the North Fork at the equivalent to NE 128th St.
A creek not named on the Alliance map is shown starting in the open at NE 143rd St, only entering culverts at NE 137th St, and going straight down 17th Ave NE either way. It later switches to 19th Ave NE but stays mostly in culverts until reaching the North Fork at the equivalent to NE 130th St. Again, topographical lines suggest the straightness isn't entirely artificial.
Topographical lines don't say much about Littles Creek in Seattle, but it's shown on the 1859 map as well as the Alliance one. It starts in Shoreline, in culverts most of the way, but is mostly in the open from the equivalent of 10th Ave NE and NE 145th St southeast, partly through Jackson Park's northeast, to 15th Ave NE and the equivalent of NE 138th St. There it returns to culverts going straight south to the equivalent of NE 133rd St.
The reason topographical lines don't confirm Littles Creek's Seattle course is that it hugs the bottom of the last northern hill, which peaks at 368 feet at the equivalents of 9th Ave NE and NE 140th St in Jackson Park. This hill is round, unlike the stretched north-south orientation of the previous three. The North Fork runs southwest of it.
The Plateau
Beyond the North Fork, both west and south, is the first and largest of the plateaux. Far north, it appears to reach from around I-5 to the tops of the Puget Sound coastal cliffs, with tall walls on east and west getting it to about 400 feet. It extends further east south of the North Fork, into Pinehurst, where the base level is lower, nearer 300 feet, although Pinehurst is a hill inside the plateau, reaching 340 feet. Its northern wall in this extension faces the North Fork all the way southeast to its easternmost point, at 34th Ave NE and NE 115th St. South of there it retreats back west quickly. Most of the way back to 1st Ave NE it's bordered by the South Fork, with the walls of Maple Leaf Hill and the next plateau beyond. Across I-5, it slopes more gradually until things like Green Lake and Phinney Ridge intrude.
Not much of this plateau drains into the North Fork, but not much of an elephant is still bigger than a mouse.
In the north the plateau continues into Shoreline, so the slopes are gentler and the topographical lines' signals of streambeds less clear. But an all-Shoreline tributary reaches close to Aurora Ave N at the city limits, and there are faint signs that Meridian Ave N lies on top of a stream that joined that creek. (At least one stream in that part of Shoreline is named Meridian Creek, but no two maps I've checked agree about which one.) Also faint are the hints of a stream starting near Sunnyside Ave N and N 143rd St, going northeast to NE 145th St, then east along the latter to the North Fork.
Smaller streams over the plateau's eastern walls are much clearer, and for a few blocks near 4th Ave NE every street seems to have been built over one: NE 140th, 139th/137th and 136th Streets, I-5 itself, one angling northeast from the equivalent of NE 132nd St. (This last seems likely to have drained at least most of Northacres Park.) There's a strong signal over a lower wall starting near 12th Ave NE and NE 125th St and heading northwest. The part of 19th Ave NE that actually goes northeast may sit in a streambed.
Only one southern tributary of the North Fork is attested on the maps, though, a short one on 125th St NE shown on the 1859 and 1908 ones.
What I'm calling the plateau actually slopes down pretty dramatically to the east, reaching 200 feet about 25th Ave NE east and continuing downhill from there. Meanwhile, as the North Fork heads south of the hills, a comparable lowland stretches north of it. Downtown Lake City is in this lowland.
The North Fork
The North Fork of Thornton Creek starts north of NE 175th St in Shoreline. It enters Seattle in culverts along I-5. Already there I suggest a hypothetical stream joining it on the right, from the plateau's eastern wall. The North Fork emerges into the open - from this point on, it's usually in the open - and enters Jackson Park. There it's the creek I told you about, dear Diary, in "The Jackson Park Perimeter Trail". I've suggested five minor streams that could have joined it from the right as it flows southeast through the park.
It continues southeast through Flicker Haven Natural Area, then turns northeast to go through Licorice Fern Natural Area. It turns because just there, between the two parks, is where it first collides with the plateau's northern wall. The first tributary from across that wall, the hypothetical stream headed northwest from 12th Ave NE, would reach the North Fork in Licorice Fern.
After that park the plateau wall, and the North Fork, turn southeast again, and continue in that direction a long way. Almost immediately the fork picks up its first left-bank tributary in Seattle, Littles Creek, then two more, the unnamed creek and Hamlin Creek. The hypothetical 19th Ave NE stream would have joined it right after the unnamed creek. After its last right-bank tributary, the unnamed historical stream, it goes through the Thornton Creek Addition, past Virgil Flaim Park, and through Homewood Natural Area.
(The Thornton Creek Addition, dear Diary, is a small place listed in the real property report that I forgot and never visited or told you about. I'm sorry. It's near 23rd Ave NE and NE 125th St.)
Anyway, the North Fork then collects the big hypothetical stream of downtown Lake City, Little Brook's littler neighbour, and finally Little Brook itself. There the plateau finally ends, and the North Fork finally turns, going south toward its junction with the South Fork.
Which, dear Diary, I hope to tell you about soon. Happy days until then.
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