01K050 – Maple Cr. @ mouth
Technical Notes - 2005 Water Year

Chuck Springer

The telemetered streamgaging station on Maple Creek at the mouth operated throughout 
the water year 2005.  A series of storm events in October and November caused fairly 
extensive flooding in the Nooksack basin, mainly in the agricultural lowlands.  The 
events resulted in the highest peak discharge in the station’s two and one half year record.  
This did not cause any noticeable changes in channel geometry or in the relationship 
between stage and discharge.  A large rain on snow event in mid January resulted in a 
lower peak discharge than the largest of the fall storms, but this caused significant 
enough changes in channel geometry to alter the stage to discharge relationship at the 
station.  Despite abundant late spring rainfall, flows at this station began dropping to 
summer low flow levels by late May.

Rating Curve

For the water year 2005, the rating curve for this station covers a range of discharge from 
0.75 cubic feet per second (cfs) to 260 cfs.  The range of stage encountered during the 
water year was 5.45 feet.  The range of discharge encountered during the water year was 
less than 0.75 cfs in September of 2005 to 259 cfs in November of 2004.  The measured 
discharge, ranging from 1.5 cfs to 168 cfs, covers only 64% of the magnitude of flows 
encountered during the water year.  However, flows rose above the measured range only 
2% of the time during the water year, and fell below the measured range only 8% of the 
time.  Flows greater than 168 cfs were modeled using the established relationships 
between stage, velocity, and cross-sectional area.  The accuracy of this model is 
considered to be within ±15%.  A large storm event in mid January of 2005 caused 
substantial scouring of the stream channel, altering the relationship between stage and 
discharge.  Another storm induced shift in channel geometry that occurred in early 
summer of 2005, but could not be isolated to a single storm event.  The shift was “phased 
in” over the course of several storm events that occurred from mid June to mid July.

Stage Record

The station logged continuously throughout the water year without interruption.  For 
most of the water year 2005, the orifice pipe for this station was embedded in a beaver 
dam.  On June 20, 2005, the pipe was relocated downstream of the dam.  The beaver dam 
introduced a great deal of turbulence to the water column; therefore, there was a great 
deal of variability between logged stage values and manually read stage values.  The 
differences between logged and manually read stage values at this station were usually 
around 0.10 feet, but was as high as 0.49 feet.  Time weighted corrective adjustments 
were made to the continuous stage record whenever the difference between logged and 
measured stage values resulted in a 5% or more difference in discharge.  All adjustments 
are documented in the Hydstra Data Workbench.  All data between July 7, 2004, and 
June 20, 2005, are considered estimates, and are qualified as such in the Hydstra Data 
Workbench.

Future Efforts

Both high and low flow measurements are needed at this station to supplement the 
established rating curve.  Also, a longitudinal channel elevation survey is planned for the 
summer of 2006.  The results of this survey will be used in the development of a velocity 
model for the stream.