Methods
In spring 2018, 10 rock weirs and 11 adjacent pool features were
established as cross-sections for monitoring at Weslie Creek. Using
real-time kinematic (RTK) GPS, a topographical survey was completed
through the reach, at each cross-section, and at each rock weir
keystone. Reach profile and cross-section elevation data were collected
by taking bed and water surface elevation points with the RTK GPS every
20 cm systematically. The rock weir keystone elevation data were
collected by taking elevation points with the RTK GPS on the surface of
the keystone and around the exposed circumference. RTK GPS produced
elevation data accurate to +/- 0.02 m. From the topographical survey,
channel and rock weir geometries, and bed and water level elevation
differences were determined.
Physical habitat conditions, including water depth and water
temperature, were monitored continuously throughout the field season
using Onset HOBO pressure transducers. One sensor was installed in a
stilling well at pool 7, and another on the adjacent right bank to
collect atmospheric pressure data, once per hour. The data were
retrieved from each sensor every two weeks to ensure data quality and
assess equipment productivity, particularly following large rainfall
events. Wolman (1954) pebble counts were completed (measuring 20 pebbles
at each pool feature) and monumented photographs were taken on a
bi-weekly basis to identify bed substrate composition at each pool, and
record changes at each pool during the field season.
Velocity measurements were collected using a three-dimensional acoustic
Doppler velocimeter (ADV) (+/- 0.01 m/s). At each pool, the ADV was
positioned in the flow at 60% depth. Velocity measurements were
collected every 10 cm from left bank to right bank (Newson and Newson,
2000; Carollo et al., 2002). At each rock weir, velocity measurements
were collected at active gap and/or over-weir flow pathways. Under
intermediate and high-water level conditions, where the gap and/or
over-weir flow pathways were larger in width, multiple velocity
measurements were collected across the pathway, and an average
“cross-section” velocity was identified for the associated pathway.
To evaluate fish passage effectiveness through the rock weirs, the
swimming characteristics of local fish species were compared to the
velocities through rock weir gap and over-weir flow pathways. The target
fish species were identified by reviewing local conservation authority
watershed and sub-watershed reports, and the swimming characteristics
for each fish species were identified by reviewing relevant literature.