High Water in Oregon

It has been raining here in Oregon for a week.  Fortunately, I am writing a report that involves some knotty problems in structural geology.  I am also watching the local streams on an on-line feature published by the City of Salem called "High Water Watch" by the firm, One Rain, Inc.

There is an interactive map that you can click to find stream depths and flows. The stream widths are less than thirty feet on average, so a stream height of five feet is quite remarkable.  The starting height is two feet. For a four  foot reading, you cannot stand in the stream.

Interested?  Put "high water" and "salem oregon" into your browser and you will be led to the online information.

The present (Let's see, December 1 the creeks started to rise with previous rains...) eleven day series of storms is very unusual.  The storms have caused a regional catastrophe of washed out roads, landslides and wholesale scenes of flooded parts of Portland and of Coast Range towns like Vernonia.  Muddy water everywhere.  A one-day rainfall record was set in Portland on Pearl Harbor Day, December 7th.  The highest water levels and greatest flows in the Salem Hills, came at lunch hour. Here is a weather satellite of the storm system at about that time.

Like any weather information by the National Weather Service, the accessible information, now, will be pushed into the past by following days of observation, so let me give you a very short list of flows on a creek in the Salem Hills. The time for each reading is 10:30 in the morning.  It just looks good to me that way.
December 5: 40.cfs , December 6: 56 cfs , December 7: 350 cfs , December 8: 177 cfs , December 9: 204 cfs , December 10: 187 cfs, December 11: 96 cfs, December 12: 104 cfs. The stream is Battle Creek at Commercial Road.

The stream drains a highland of weathered basalt (basalt is dark gray or black igneous rock, an extrusive).  The upper reaches of the creek drain a rural area, that accounts for about 20 square miles.  A tributary, Waln Creek, drains another 6 square miles of suburban land.  At the time of the height of the flood, another gage on the rural stem read 100.45 cfs.  The combined rural/suburban gage read 389.90 cfs, so there was a greater contribution of runoff from impervious cover of streets and parking areas.

On a visceral level, the December 7th flood was wild.  Without the measurements, it demonstrated the nature of a catastrophe.  There are unusual sights, in my case, water forming as small ponds on my lawn or Battle Creek flood waters sliding around a tight curve in the stream bed on Rees Hill Road like a water slide ride at the now defunct Thrillville Water Park.

Disclaimer:  No bridges were washed out in the Salem Hills by this event.  Car access was safe and I did not wade in any creeks. I took notes, a few pictures and went and had coffee.