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5. LABORATORY TESTS OF SILT FENCES AND A ROCK BERM
5.1 Flume Tests
The sediment removal performance for the two most common temporary controls
in the inventory, silt fences and rock berms, was investigated under control conditions in
an outdoor flume. Monitoring controls in a flume allowed control over such variables as
the influent flow rate and TSS concentrations. Data were collected using simulated
runoff events in the flume. The hydraulic characteristics of these controls also were
evaluated.
5.1.1 Flume and Bulk Water Delivery System
An outdoor flume at the Center for Research in Water Resources (CRWR) was
used as the test bed for the sediment control experiments. The steel flume was 61-m-long
with a cross-section that is 0.76-m wide and 0.6-m deep. The slope of the flume is
approximately 0.33 %. A 10-cm sand and gravel bed was used to simulate field soil
conditions. The thin layer of highly permeable soil allowed some infiltration, which
might be expected in the field. The flume and water delivery system used for the
sediment control tests are shown in Figure 5.1.
Bulk water was circulated through the elevated water tank near the head of the
flume. The water level in this tank was sufficient to drive the simulated runoff through
the mixing tank, flume, and sediment controls. Water for each test was drained from the
elevated tank, over a V-notch weir and into the rapid mixing tank at the head of the
flume. A constant head in the elevated water tank was maintained to provide a constant
flow rate to the mixing tank.
The V-notch weir allowed the measurement of the bulk water influent flow rate
into the flume. The weir was calibrated by filling a sealed section of the flume at
different flow rates and monitoring the rate of change of the water level. The product of
the constant surface area of the test section of the flume and the rate of change of the level
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