Mills Creek drainage viewed from the west
Mills Creek drains off the west side of Anderson Mountain in the Northwest Cascades down to the Samish River valley. Mills Creek is one of several drainages that have built alluvial fans onto the Samish River valley floor.
Mills Creek alluvial fan is the southernmost fan in this DEM
The valley floor is colored with dark green being the lowest elevation and light browns mark the apex of the alluvial fans that have built up in the valley
The Samish River is a rather small river and by northwest standards falls into a category of creek like except it is rather long and has an important salmon fishery. Its valley in the Northwest Cascades predates the river. The Samish just happens to be occupying this deep intermountain valley.
The Samish flow and gradient is no match for the episodic discharges of sediment from the tributary streams flowing off the steep slopes of the valley. These tributary fans are blocking the Samish and have formed a chain of lakes and swamps along the gentle valley floor.
Lake/swamp formed up stream of the Mills Creek alluvial fan
Mills Creek has a bit of sad history. A landslide in the creek drainage blocked the creek and the subsequent dam burst debris flood killed a resident on the fan below during a storm event in January 1983.