River & Physical Modeling Experience - David L. Derrick
For 19 years Mr. Derrick was the principle investigator on many
physical movable-bed model studies involving some of the most
hydraulically complex reaches of the Mississippi River. These research
projects have involved the application of various river training
structures to solve a number of environmental, navigation, and dredging
He was instrumental in the development and implementation of the
Bendway Weir methodology for navigable rivers, non-navigable rivers,
streams, and very small streams.
A Bendway Weir is an upstream-angled underwater sill. Water flowing
over the weir is redirected at an angle perpendicular to the weir. When
the weirs are angled upstream water is directed away from the outer
bank and toward the inner part of the bend. The river’s
secondary currents in the bend are broken up. Weirs are typically built
in sets (4 to 14 weirs per bend) and are designed to act as a system to
capture, control, and redirect current directions and velocities
through the bend and well into the downstream crossing.
Both model (since 1988) and prototype (1989) results indicate that
construction of a series of Bendway Weirs in the navigation channel of
a bend results in the following improvements: the navigation channel
through the bend and immediate downstream crossing is widened and
better aligned, deposition occurs at the toe of the revetment on the
outside of the bend (increasing bank stability), surface water
velocities are more uniform across any specific cross-section, flow
patterns in the bends are generally parallel with the banks (not
concentrated on the outer bank of the bend), and the thalweg of the
channel is moved from the toe of the outer bank revetment to the stream
ends of the weirs.
Using a physical movable-bed model, Mr. Derrick first explored and
analyzed the multiple benefits of Bendway Weirs on two bends of the
middle Mississippi River. Prototype Bendway Weir plans (and
construction sequences) for these bends (Price’s Landing and
Dogtooth) were developed using this model. Since 1989 over 190 weirs
have been built in 22 bends of the Mississippi River. Prototype
improvements have exceeded the results obtained from the model study.
Andy Cannava of American Commercial Barge Line said “This is
best thing to happen on the river in a hundred years”.
of the 5 oldest weir installations show that from 1990-95 dredging was
reduced by 80%, saving $3,000,000. In addition, towboat accidents were
reduced, tow delay times at bends were reduced, sediment and ice
management were improved, Least Tern (an endangered species) nesting
areas were undisturbed, aquatic habitat area was increased, and fish
size and density in the weir fields dramatically increased.
This model study and associated prototype projects have revolutionized
river training structure conceptualization and thinking to such an
extent that St. Louis District present and future river plans almost
exclusively involve Bendway Weirs. The weirs represent a unique and
innovative solution to a perplexing set of problems in a number of
bends where traditional solutions were not applicable.
Mr. Derrick has served as the principal investigator or designed all
weir plans on the following Mississippi River physical movable-bed
model studies that involved testing of Bendway Weirs: Greenville Bridge
(improvement of current sets through a highway bridge navigation span),
Memphis Harbor (shallow-draft navigation improvement), Old River
(sediment diversion and navigation improvement), Redeye Crossing
(deep-draft navigation improvement and protection of docking
facilities) and St. Louis Harbor (improvement of navigation current
sets through a series of six highway bridges). Mr. Derrick also tested
weirs on the Montgomery Point reach of the White River (improvement of
navigation approach channel to a lock and dam) and a small sand-bed
stream model involving one unrevetted bend. In addition he assisted
with the following movable-bed model studies: New Madrid, Old River
(Fixed and Movable-bed), Kate Aubrey, Groins and Dikes Research, Lock
and Dam 26, Redeye Crossing, Loosahatchie-Memphis Harbor, White River,
and Buck Island.
Mr. Derrick designed a computer controlled automated sediment feeder to
introduce coal into movable-bed models and assisted with the Redeye
Crossing numerical and Greenville Bridge navigation modeling efforts.
Mr. Derrick conducted a four year Navigation Hydraulics research work
unit, “Hydraulic Design of Bendway Weirs”,
expanding the envelope of knowledge of weir design in navigable rivers.
Mr. Derrick was the principle investigator in a four year REMR (Repair
Evaluation, Maintenance and Rehabilitation) research work unit which
inventoried all currently maintained Corps river training structures
located in shallow-draft non-tidal influenced waterways (over 10,000
structures). This work documented all past dike repair work, recorded
all current dike repair methods, evaluated all new technology related
to the field of dike repair, and formulated guidelines for structure
inspection, record keeping, evaluation, and repair. Results from this
research unit were recorded in three REMR technical reports.
During 1997-2000 Mr. Derrick headed a team tasked with designing a 10
mile long innovative, cost-effective, bank stabilization project on a
section of the laterally unrestrained Red River between Denison Dam and
Index, AR (TX-OK border). Construction costs were estimated at 4-8
million dollars, less than one-half the cost of conventional bank
protection. Mr. Derrick designed a 5-year monitoring program to assess
the performance of this proposed project.