01N060 – Bertrand Cr. near mouth
Technical Notes:  2005 Water Year

Chuck Springer

The telemetered streamgaging station on Bertrand Creek near the mouth operated 
throughout the water year 2005.  A series of storm events in October and November 
of 2004 caused fairly extensive flooding in the Nooksack basin, mainly in the agricultural 
lowlands.   These events, while not channel-changing events, resulted in the highest flows 
recorded at this site in three years of record.  A wetter than normal early summer resulted 
in a minimum summer flow of 2.7 cubic feet per second (cfs); five times higher than the 
minimum summer flow for the previous record in the past two years.

Rating Curve

The range of discharge encountered during the water year was from 2.7 cfs in August of 
2005 to 647 cfs in November of 2004.  The range of stage encountered during the water 
year was 11.7 feet.  The measured discharge, ranging from 1.0 cfs to 318 cfs, covers less 
than 50% of the magnitude of flows encountered during the water year.  However, 
discharge rose above the measured range of flows only 5% of the time during the water 
year.  All low flows during the water year 2005 were within the measured range.  Flows 
greater than 318 cfs were modeled using the established relationships between stage, 
velocity, and cross-sectional area.  The accuracy of flows derived from this model is 
estimated to be within 20%.  During a storm event in late August 2004, several pieces of 
wood debris were deposited downstream of the gage.  This caused stage levels to become 
elevated, altering the relationship between stage and discharge.  During a subsequent 
storm event in early October 2004, the debris was transported downstream, returning the 
relationship to normal.  The rating curve was shifted to reflect both of these events.

Stage Record

The station logged continuously throughout the water year without interruption.  Due to 
periodic sedimentation at the station site, coupled with inherent difficulty in reading the 
staff gage in high flow conditions, differences between logged and manually read stage 
height values were encountered throughout the water year.  These differences were 
typically between 0.01 feet and 0.04 feet, but were as high as 0.61 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.  In an effort 
to address the periodic sedimentation issues at the site, the gas bubbler system was 
programmed to purge the orifice line daily.

During a large rainfall event in mid January of 2005, Bertrand Creek became backed up 
from the Nooksack River.  Stage height at this site was elevated to the extent that 
Rathbone Road was under more than a foot of water.  Since the relationship between 
stage and discharge was compromised due to these two factors, data during this time 
period was qualified as estimates.

Future Efforts

Cross sectional and longitudinal surveys of this site are planned for summer 2006 to aid 
future modeling efforts.  Additional high flow measurements are also needed to 
strengthen the upper segment of the rating curve.  Future high flow measurements will be 
taken using an acoustic Doppler current profiler (ADCP), which will increase the range 
of conditions under which discharge measurements can be taken at this site, as well as 
improve the accuracy of these measurements.