Hydraulic Cover Stones (HCS)

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Hydraulic Cover Stones (HCS)
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THIS METHOD IS A DAVE DERRICK DISCOVERY
(DDD)
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Hydraulic Cover Stones (HCS)

• Hydraulic Cover Stones (HCS) are
  typically large single stones placed in a flowing
  channel with the crest of the stone within inches
  of the base flow water surface elevation.
• The constant movement rippling of the water
  from the Hydraulic Cover Stones results in a type
  of cover, hydraulic cover, masking fish
  location from the view of predators. The stones
  also provide resting areas within-channel
  refugia for fish during high energy, high-flow
  events.
• Hydraulic Cover Stones are
  especially useful in sections of the stream with
  little in-channel structure, or vegetative cover,
  or undercut banks.

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Hydraulic Cover Stones (HCS)

• Large single stones placed in a
  flowing channel. Three versions
• 1.) Top of the stone set at an elevation slightly
  lower than the typical base-flow water surface
  elevation. When sited correctly, the accelerated
  flow over the top of the stone will change from
  subcritical to supercritical flow, immediately
  downstream back to subcritical (usually with a
  weak hydraulic jump). The hydraulic jump will
  entrain air help aerate the stream.
• 2.) Stone crest set just below the base flow
  water surface elevation results in an
  acceleration of the water moving over the top of
  the stone, with standing waves (stationary
  waves) forming downstream of the stone.
• 3.) Stone crest set slightly above the base flow
  water surface, resulting in a V-shaped wake and
  flow split with a double return eddy flow pattern
  DS of the stone. However, these emergent stones
  might be used as perches for predators.

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Hydraulic Cover Stones provide improved aquatic
habitat
Hydraulic Cover Stones shown functioning 3
different ways. Graphics courtesy of Ecology
Environment, Inc.
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UNKNOWN AGE Looking US _at_ a boulder acting as a
HCS. Split flow, acceleration, air entrainment,
dead water DS of boulder.
UNKNOWN AGE CEDAR RIVER, SEATTLE, WA-DERRICK
8-22-2012
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Functions of Hydraulic Cover Stones

• Provides micro-topography (scour deposition)
• Provides diversity of velocities
• Provides hydraulic cover turbulence, surface
  water disturbance (boat wake), return currents,
  eddy fences, internal distortion, pressure zones,
  undulating surface water, standing waves, etc.
• Provides feeding lanes for fish
• Provides shape cover solid substrate for
  benthics
• Provides refugia during high flow events
• Dissipates energy
• Can aerate water, or de-gas super-saturated water

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Boulder Clusters typically consist of a number of
very large stones closely arranged in some type
of pattern. The Boulder Cluster usually blocks a
fair amount of the stream, with stone crest
heights 2 to 3 ft above the base flow water
surface elevation. Hydraulic Cover Stones are
single large stones with the crest heights within
inches of the base flow water surface elevation.
HCS block a very small percentage of the
cross-section of the stream.
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• Some concerns with Boulder Clusters (cluster too
  wide tall here in a high bed-load stream)

Shadow depositional sand bar splits flow,
resulting in both banks eroding in a straight
stretch. Little Sugar Creek one year after
placement (1998). This was not the designers
intent.
(Purloined from Andrew Burg)
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• Possible Problems with Boulder Cluster designs
• 1. Excessive scour buries boulder
• 2. Cluster blocks large percentage of stream
  flow
• 3. Cluster redirects stream energy in unwanted
  direction (s)
• Excessive deposition DS of cluster
• Cluster too high, provides perches for
  predators/fishermen

(www.E-senss.com)
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Natural Hydraulic Cover Stones (HCS) on the
Genesee River, Letchworth Park, NY photo taken
2003.
Flow
Hydraulic Cover Stone at Elton Creek, NY
Flow
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Hydraulic Cover Stones on Eighteenmile Creek
Project, Newfane, NY(constructed Sept. 2003)
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My sneaker
Close-up of large stones to be used as HCS, these
were hand selected, minimum 3 ft by 3 ft.
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A Hydraulic Cover Stone (HCS) dug into the stream
bed substrate for stability. The downstream wake
is the Hydraulic Cover.
Flow
HCS
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In a sand-silt bed stream, deeper excavation, or
reinforcement of the substrate, might have to be
accomplished so that bed scour does not cause the
HCS to sink into the substrate.
Flow
HCS
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Here comes Jimmy with a Hydraulic Cover Stone
(HCS)!! Water depths were measured the correct
thickness of stone selected for this specific
location
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Water depth was measured, a specific sized rock
delivered
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Carefully placing the Hydraulic Cover Stone
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Bed was dug stone placed in hole. Sediment
near stone acting as a dye trace.
Flow
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First HCS placed in Eighteenmile Cr., turbulence,
energy dissipation, eddy fences
Flow
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Looking DS, note locations of Hydraulic Cover
Stones during unusually low flow conditions
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Crazy turbulence surrounds a HCS
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Trio of Hydraulic Cover Stones working
beautifully, note those wakes (the hydraulic
cover)
Locals say this is the best fishing area in the
creek (US of Cover Stones)
This is a cobble-bed stream. This technique might
not work as well in a sand-bed stream (stones
could subside)
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HCS using up stream energy entraining air into
flowing water
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Flow from left to right, note the hydraulic jump
_at_ the Hydraulic Cover Stone
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Same Hydraulic Cover Stone, close up
Looking US at a Hydraulic Cover Stone
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Multi-Use Hydraulic Cover Stones, in this case a
fishermans resting rock, (FRR)
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Salmon fishermen concentrating efforts among
the Hydraulic Cover Stones, Eighteenmile Creek,
Newfane, NY, Oct 2003
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Fish those Hydraulic Cover Stones !!!!!!!!
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(FISH ON !!!)
NO NEED FOR A NET (if youre good)
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On Saturday 10-19-03 (during the salmon run)
folks are everywhere, 353 recreators by 930am.
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Hydraulic Cover Stones on Cattaraugus Creek
_at_ Savage Road, Sardinia, New York
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Hydraulic Cover Stones for stable pre-dug
Pocket scour holes in shallow areas (riffles
shallow runs)

• Increases depths
• Provides microtopography
• Provides diversity of velocities
• Provides hydraulic cover
• Provides shape cover
• Provides in-channel refugia
• Dissipates stream energy

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Catt Creek, looking US at riffle-run, measuring
how high the Hydraulic Cover Stone will jut into
current.
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Hydraulic Cover Stone in pre-dug scour hole,
stones measured to fit
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Looking US at a series of Hydraulic Cover Stones,
took 50 minutes to install 9 stones
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Looking DS at same Hydraulic Cover Stones located
in run section of stream. Previous condition
was shallow sheet-type flow
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Mini-Case Study 1 of 3
Stone is here
A close look at a hard working Hydraulic Cover
Stone during a high water event, Cattaraugus Cr.
at Savage Rd. 11/4/2004
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But relatively calm right at the Hydraulic Cover
Stone, energy dissipated!!
Mini-Case Study 2 of 3
Downstream of HCS fierce currents (water piling
up on hip boots bent pole)
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Mini-Case Study 3 of 3
Same Hydraulic Cover Stone during base flow
conditions, not very impressive considering
observed function during high flow
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Hydraulic Cover Stone Quick Dirty Flume
Tests _at_ UB
On 11-11-2010 a series of short test runs were
performed on a small 4 inch wide sand-bed
hydraulic flume _at_ the State University of New
York at Buffalo (UB). Flow duration ranged from
20 minutes to 45 minutes or so. Flow stage was
supposed to mimic the Q-2 flow, but varied when
we forgot to turn on the inflow hose add water
as the flume leaked. Our feet got wet.
Discharge was varied a bit not written down.
Otherwise very scientific!!
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Looking US _at_ the flume flume-meister, Dr. Sean
Bennett
SEAN BENNETTS FLUME _at_ UB ENTIRE FLUME - PIX
DAVE DERRICK 11-11-2010
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THE EFFECTS OF STONE SIZE ROUGHNESS ON
NEAR-FIELD SCOUR AROUND A SINGLE HYDRAULIC
COVER STONE
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Looking _at_ 3 Hydraulic Cover Stones. The upstream
stone is small aerodynamic resulting in very
little scour. More scour as each downstream HCS
is progressively larger blocks more flow
SEAN BENNETTS FLUME _at_ UB HYDRAULIC COVER
STONES-DERRICK 11-11-10
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Looking _at_ a single HCS. The US face of the stone
is square vertical. Scour was so great US of
the stone that it fell US into its scour hole!!!
LESSON SIZE SHAPE MATTER GREATLY!
SEAN BENNETTS FLUME _at_ UB HYDRAULIC COVER
STONES-DERRICK 11-11-10
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This PowerPoint presentation was developed
built by Dave Derrick. Any questions or
comments, call my personal cell _at_ 601-218-7717,
or email _at_ d_derrick_at_r2d-eng.comEnjoy the
information!!
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Speaking of size, presented here is Jackson
Danger Rainer wearing Uncle Brents huge size 14
sneakers