Patent Application
20200256025
This invention has been created without the sponsorship or funding of any federally sponsored research or development program.
This invention involves a system for allowing riverine fish to bypass river obstructions such as dams.
Prior systems for assisting fish in navigating around river obstacles, such as dams, is generally only effective for the strongest swimming fish such as salmon. Furthermore, prior systems are very expensive, complex, inefficient, and difficult to install, to use, and to maintain.
These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of some embodiments of the present invention to provide a system for assisting fish to pass around river obstruction in an efficient and effective manner.
Another object of some embodiments of the present invention is to provide a fish ladder that can be used effectively by weak swimming fish.
A further object of some embodiments of present invention is to provide a fish ladder that is easy to design
It is another object of some embodiments of the present invention is to provide a fish ladder that is inexpensive.
It is a further object of some embodiments of the present invention to provide a fish ladder that is easy yo install and maintain.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto, it being understood that changes in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention.
A fish ladder for allowing fish to pass upstream around barriers in rivers, in which a water carrying channel carries water from above a barrier in a river to below the barrier. The channel has a first sidewall and a second sidewall and a plurality of baffles, attached to each sidewall and extending into the channel. The dimensions of the baffles, and the arrangement of the baffles with respect to the channel and to each other allows the fish ladder to be navigated by less-than-strong swimming fish. The baffles alternate from one side to the other, and extend upstream from the side walls.
The character of the invention, however, may best be understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:
7. SUMMARY: Development of fish ladders in the USA has traditionally focused on passing salmonid and other strong swimming diadromous fish species over dams that stop upstream migrations, usually to spawning habitat. Recent information indicates most riverine fish species also migrate and need passage over dams to complete natural migrations and remain connected to spawning, foraging, and refuge river reaches during their life history. However, fish ladders are not available that pass most riverine fish with a moderate swimming ability, particularly small species. The fish ladder invention described in the application (an Alternating Side-Baffle Ladder=ASBL) was developed in our hydraulic lab using a straight 1 ft wide×1 ft high×21 ft long scale model (13 ft center section on an 8% slope) and later with a 13.5 ft long curved section added, total ladder at 8% slope=25 ft. Within the physical dimensions of the open flume (1 ft wide×1 ft high), we used trial and error methods to test combinations of five additional physical factors (ladder slope, side baffle length, slot width, distance between baffles, baffle angle to the wall to create a ladder design that produced two major characteristics of an ASBL: 1) a moderate velocity in baffle slots (12-17 inches/sec away from the outside wall in the scale model), and 2) a large slow velocity eddy between any two baffles that provided fish an easy movement route and a resting area, and also, provided only a short distance to move through a baffle slot between two eddys. Tests with five species of locally captured wild riverine fish found many ascended the straight ASBL. Additional tests were done with six fish species in the straight ladder plus a 180° curve and two 90° curves (all 4-ft diameter) total length 25 ft. Velocity measurements found baffle slot velocities in the straight section and in the 180° curve section were similar with zones of 12 inch/sec velocity that should allow fish as small as 4 inches long to ascend. Many fish ascended the 25 ft long straight+curve ladder with 33 side baffles. The invention passed non-salmonid fishes, even small species 4 inches long. We used the same design principles as used for the scale model to design a 2 ft wide×2 ft high×70 ft long ASBL prototype ladder that was large enough to pass migrant riverine fish ? 24 inches long over the 5 ft high Stockdale Dam, Eel River, Ind. The prototype ASBL ladder had several straight sections, two 180° curves, and one 90° curve (all 12 ft diameter curves; was constructed of 3/16″ plate steel; and was composed of 11 modular sections for assembly on site. We fabricated and shipped the 11 sections of the prototype to Indiana and assembled the ladder at the dam in 10 hours in August 2017. Cooperators continued work for another week to install concrete entrance and exits for the ladder and to encase the sides of the ladder in concrete to prevent erosion by the river. In September and October 2017, cooperators from Manchester University, North Manchester, Ind., reported on three days seeing thousands of fish ascending to the top of the ladder. Capture of these fish found 12 species from 2 to 8 inches long, most about 4 inches long. Fish ascended to the top of the ladder in only 5 inches of water depth in the ladder due to low discharge in the Eel River. This is the first fish ladder design in North America to pass small non-salmonid riverine fishes with a moderate swimming ability. Larger ASBLs that pass a diversity of large non-salmonid riverine fish species can be developed using the six physical factors and relationships used for the invention. The invention provides a new tool for fish passage at barriers in North America and other countries that could improve riverine fish restoration.
8. Background on Fish Ladders Available to Pass Non-Salmonid Migratory Fish and Sturgeons at Dams in the USA
A. Focus on strong swimming fish for fish ladder design in the USA.—The USA and Canada have historically concentrated on designing ladders for powerful swimming and jumping anadromous fish migrants (species that grow to maturity in the ocean and migrate up freshwater rivers to spawn, primarly species of salmonids, i.e., Pacific or Atlantic salmon (a priority federal resource) or trout; Clay 1995). Also, in the Northeast USA, these fish ladders are used to pass powerful swimming anadromous river herring and American Shad (Clay 1995; Haro and Castro-Santos 2012). This development is reasonable to conserve anadromous fish (a federal resource) that crosses state boundaries.
Thus, the focus on powerful swimming anadromous fish lead to ladders with high water velocity that excludes most non-salmonid fish, most of which have a moderate swimming ability (Katopodis and Gervais 2010. A need for a fish ladder for moderate swimmers is particularly critical for protected riverine fish species and for small endangered or protected species (<6 inches long). Riverine fish species comprise the greatest percent of endangered vertebrates (Riccardi and Rasmussen 1999) with blockage of migrations and segmentation of populations by dams a major factor causing the decline of these fish.
At the Columbia River salmonid fish ladders in Washington, USA, recent corrections were made to the ladders to enable passage of adults of three species of federally protected lampreys, which have a moderate swimming ability (http://www.fpc.org/lamprey/lamprey_home.html). This is only one example of the insufficient design of traditional salmonid fish ladders to pass non-salmonid fish.
B. Denil and Steeppass full-baffle fish ladders.—These are two fish ladders, typically ? 3-4 ft wide) designed to pass salmonid fish (Clay 1995). They have been installed in Canada, the USA, and France on small rivers with low-head dams (? 30 ft head). The Denil ladder is constructed of wood, metal, or concrete, but the Steeppass is metal. Both are relatively inexpensive compared to large concrete ladders.
The Denil ladder was initially introduced in 1909 and was further developed by White and Nemenyi (1942); thus, it has been many decades and much learned about fish behavior since the introduction of the Denil ladder. The standard Denil has a series of baffles that extend into the ladder channel at 90° from each wall and upward from the bottom (
The Alaskan Steeppass ladder, like the standard Denil has full baffles that are parallel, but in the Steeppass ladder, all baffles are angled upstream at 45° (
Hydraulic studies of Denil and Steeppass ladders show that only the area in the bottom center of the channel (away from the baffles) has slower velocities and less turbulence that enable some fish to ascend the ladder (Katopodis 1991). The high amount of turbulence that is characteristic of both ladders is a foreign environment to wild fish, so many fish species do not enter either ladder. A Steeppass ladder was recently evaluated for passing all migratory fish in a river in North Carolina and it only passed some of the two most powerful swimming species and none of the moderate swimming species (www.fws.gov/steepassevaluation/). Both Denil and Steeppass ladders are often installed in sections (a modular design) as a cost savings.
Two additional major limiting factors against using Denil ladders are 1) they operate over a small variation in water level at the upstream ladder exit (Larinier 2008), and 2) the turbulent flow and ladder baffles make it likely that a fish pausing ascent or moving downstream can be killed or damaged by striking the baffles. This second factor is important when the fish using the ladder has federal or state protected status. The Denil and Steeppass full-baffle fish ladders were designed for powerful swimming salmonids that ascend a ladder without stopping; however, studies on six non-salmonid fish species ascending a fish ladder found much up- and downstream movement before fish finally reached the top of the ladder (Kynard et al. 2012). In turbulent Denil and Steeppass ladders, fish with this behavior could be entrained in the current, strike baffles, and be injured or killed. Thus, these ladders are not suitable for non-salmonid fish, which are the fastest growing group of endangered vertebrates on Earth (www.iucnffsg.org/freshwater-fishes/major-threats/).
The Steeppass Ladder is fabricated of metal sections (modular design) and is available from Sheepscott Machine Works, Newcastle, Me. The company estimates the metal modular design is about 20% of the cost of a traditional concrete fish ladder (www.sheepscotfishways.com/ourproduct/).
Abundant data exists that shows salmonid fish ladders are poor at passing non-salmonid fish species at dams (review by Mallen-Cooper and Brand 2007). Indeed, fish elevators in the USA at several large dams on the East coast are more successful passing salmonid and non-salmonid fish (including sturgeons) than any salmonid fish ladder (Moffitt et al. 1982; Kynard 1998; unpubl. data). If operated spring and summer, the fish elevator at the 65 ft high Holyoke Dam, Conn. River, Mass., passes the entire migratory riverine fish community including sturgeons (US Fish & Wildlife Service Connecticut River Coordinator www.fws.gov/r5crc/; B. Kynard and D. Pugh unpubl. data). However, fish elevators are only suitable for large-scale high dams (Kynard 2008), which does not solve the problem for passing non-salmonid fish at small-scale low-head dams (<30 ft high).
C. Need for a fish ladder to pass sturgeons and non-salmonid fish.—Upstream spawning migrations of all anadromous or freshwater species of sturgeons occurs annually (LeBreton et al. 2004); however, there is no fish ladder that passes adult sturgeons upstream over any dam (Jaeger et al. 2016). The best success passing sturgeons at dams in the USA or Russia has been using fish lifts (elevators) at high dams (Kynard 1998, 2008) or using a semi-natural ramp over a low-head dam (example, Lake Sturgeon; Aadland 2010). Both of these methods are expensive.
Most non-salmonid riverine fish migrate to forage, spawn, or seek refuge during their life (review by Lucas and Baras 2001). Many of the migrations are upstream and the estimated percent of migratory riverine fish species is about 80%, indicating most riverine fish species migrate (Lucas and Baras 2001). These migrations can be blocked by dams, which also, segments fish populations, which can lead to population extirpation.
Fish passage for riverine fish has developed successfully at low-head dams on small rivers in Germany and Austria by the extensive use of semi-natural bypasses, not fish ladders (DVWK 2002). This method of passing riverine fish has not developed in the USA, possibly due to the high cost of facilities.
Most non-salmonid fish, like sturgeons, have a moderate swimming ability (Katopodis and Gervais 2010) that enables fish to move upstream past natural rapids and fast water river reaches during migrations. This moderate swimming ability should allow fish to ascend a properly-designed fish ladder using a prolonged swim mode=the swimming ability to maintain position against a water velocity of 1-2 body length/sec for 20 sec-30 min (Katopodis and Gervais 2010). Thus, for a 6 inch long non-salmonid fish swimming in the prolonged mode, a water velocity in the ladder of about 12 inches/sec should allow the fish to ascend for a brief time or short distance between resting areas.
A fish ladder is particularly needed for rivers with small-scale low-head dams. The U.S. Army Corps of Engineers estimates there are 80,000 dams ? 8 ft high in the USA and almost none have fish passage. This number does not include the estimated thousands of “small unregulated dams”, ? 6 ft high that occupy a large percentage of the total number of dams on small rivers in the USA (www.americanrivers.org/). Migrations of non-salmonid riverine fish are typically totally or partially blocked by any dam ? 6 ft high.
In summary, most of the small dams on rivers of the USA will likely be removed for various reasons. However, the few dams that remain should have a fish ladder to provide natural connectivity for riverine fish populations and prevent segmentation of fish populations. Presently, no fish ladder is available to pass sturgeons or small non-salmonid fish species over dams or natural barriers in the USA. Passage of non-salmonid fish at low-head dams in the middle of the USA has been developed but is restricted to a few rivers whose dams have expensive semi-natural bypasses or river ramps (Aadland 2010).
In the USA, there is a national fish conservation need in rivers for a fish ladder that will 1) pass sturgeons and non-salmonid fish that allow ascending fish to swim upstream or downstream (without injury and loss of upstream migration drive), 2) creates maximum water velocity zones in the ladder that allow fish with a moderate swimming ability to ascend, 3) provides resting areas within the ladder, and 4) is affordable, i.e., is adaptive to the reduced funding for fish passage in the 21st Century. When cost per ladder is reduced, many more ladders can be installed.
9. Testing Spiral Alternating Side-Baffle Ladders for Passing Sturgeons
A Canadian business, Aeroceanics Fishway Corporation, designed and used a small spiral alternating side-baffle fish ladder in experiments to pass adult sockeye salmon in Canada in 1974 (Biette and Odell 1976) and salmon and trout in 1976 (Tredger 1982).
Although the Aeroceanics' ladder velocities were too fast for non-salmonid fish, two physical characteristics of the ladder seemed appropriate for non-salmonid fish with a moderate swimming ability: 1) no cross walls to stop fish ascent, and 2) an ascent route through a series of vertical slot openings that alternate from side to side. Both of these features were preferred by two species of sturgeons during observations in fish ladders, including a spiral alternating baffle ladder (Kynard et al. 2002, 2008).
From 1999-2002, with funds from the US Corps of Engineers, Boyd and his research team observed the swimming ability and behavior of juvenile Pallid Sturgeon and Shovelnose Sturgeons in a short spiral ladder with three alternating side-baffles (Kynard et al. 2002).
From 1999-2005, with funds from the Great Lakes Fisheries Commission and the Menominee Tribe of Wisconsin, Boyd and his team constructed a large (39 inches wide×39 inches tall) experimental spiral alternating side-baffle fish ladder on a 6% slope and tested juvenile and adult Lake Sturgeon, adult Shortnose Sturgeon, and non-salmonid adult fish from the Connecticut River and elsewhere for behavior and passage success.
However, passage success of fish in the spiral ladder only occurred at a low flow=low water depth (11 inch gage height) and had a high mean baffle slot velocity of 3.8 ft/sec, a velocity regime far too fast for fish with a moderate swimming ability. Fish did not ascend at greater water depths=greater flows=greater baffle slot velocities. Further, a problem with the basic design of a spiral ladder was that the ladder loops superimposed on top of each other created an obvious maintenance problem for removing river debris. Thus, the spiral alternating baffle design did not result in a useful fish ladder.
10. The Invention: R&D to Develop a Non-Spiral Alternating Side-Baffle Fish Ladder for Riverine Fish with a Moderate Swimming Ability
Boyd (Research Fish Biologist, GS-14; Biological Resources Division, U.S. Geological Survey) retired from the federal government in 2007. In 2008, he started a private company, BK-Riverfish, LLC, a migratory fish behavior-fish passage consulting company. In 2014 with funds from the company, Boyd and Brian (fish biologist and son) with assistance from a Brazilian hydraulic engineer, Ricardo Junho, Ph.D., began a final R&D effort to determine if an Alternating Side-Baffle Ladder (hereafter, =ASBL) could be developed for non-salmonid fish with a moderate swimming ability. We wanted to develop a fish ladder with acceptable velocity and flow conditions that could be used in any river in any country and for any community of riverine migratory fish given restrictions on size of fish (<24 inches long) and swimming ability of the smallest anticipated fish (4 inches long and about 12 inches/sec velocity; Table 1) likely to use the ASBL. Because 4 inch long fish cannot swim in the fast velocity used by a 24 inch fish, we selected the approximate velocity needed for a 4 inch fish as our velocity target during R&D testing.
Swimming ability of fish is well-studied (review, Beamish 1978) and in a simple laminar flow, like swimming ability is commonly measured, it is common for fish to be able to maintain position in water with a velocity of 10 body lengths/second (BL/s) for <20 sec (burst swimming mode; Beamish 1978). However, flows in a fish ladder are complex with micro-vortexes, not laminar, and during ascent through a baffle slot, fish swimming movements are responding to changing velocities, other fish present, etc. Trials with small fish, including small fish with a moderate swimming ability like juvenile sturgeons, have shown that some can only ascend a fish ladder in water velocities of about 3 body lengths/sec (Kynard et al. 2002, 2008). Thus, to be conservative and certain our ASBL could pass 4 inch long fish swimming in their best burst swimming mode, we set the minimum target velocity for R&D tests, at 3 body lengths/second or 12 inches/sec. Table 1 shows the water velocity that fish of various body lengths can likely ascend in our fish ladder.
After building a hydraulic system consisting of a sump tank water reservoir, a sump pump and pipe to supply a large energy diffusion head tank, R&D was done in a channel 1 ft wide×1 ft full water depth. Initial R&D used the ladder on 10% slope, but changes in baffles could not reduce slot velocity to desired level, so we lowered the ladder to 8% slope and used this slope to develop the invention. We developed both straight and straight+curved scale models. First, from December 2015-June 2016, in a 21 ft long straight channel (13 ft long straight section ASBL (# side baffles=18). We tested the ladder on 10% initially, but lowered the ladder to 8% slope to get target slot velocities. After successful hydraulic tests in the straight ASBL with 8% slope, we tested fish in July 2016 and found many ascended. Thus, in August-September 2016, we replaced the top of the straight section with a 4 ft diameter 180° curve and two 90° curves, making a straight—curve ASBL 25 ft long with 33 side baffles on 8% slope. The curve was added to insure average slot velocities in straight and curved ladder sections were similar. Thus, in October 2016, we tested riverine fish ascent in our straight+curve ladder, a configuration likely required for a ASBL with switch-backs to ascend a ground slope >8°. During most R&D trials, water depth in the ladder was 12 inches, or channel full, a hydraulic condition that caused high baffle slot velocity along only the outside wall (
The hydraulic objective of R&D trials in the straight ASBL was to create a 12-17 inch/sec velocity regime in baffle slots, a velocity that should allow fish of 4 inches body length to ascend using their burst swimming ability of a minimum of 3 body lengths per second. After testing slot widths of 4 to 6 inches wide, we obtained the target velocity range with a 5 inch wide baffle slot and baffle spacing that was 5 inches from baffle tip to the next baffle. We estimated a slot width of 5 inches would pass all non-salmonid fish species of body lengths 4-24 inches long likely to migrate in the Eel River, Ind., at Stockdale Dam (pers. comm., Jerry Sweeten, PhD, Head of the Biology Department, Manchester University, N. Manchester, Ind.).
Trials in a scale model with 1 ft wide×1 ft high physical dimension, our physical R&D tests used combinations of five additional physical factors to obtain the target water velocity regime in baffle slots: 1) baffle design (7 designs tested) all with the baffle facing upstream, 2) angle of baffle to the wall (initially 90°, like the earlier spiral baffle design, then after 90° created too fast slot velocities, 65° in the straight reach and <60° at baffles on the inside of curve, 3) baffle slot width (6 inches initially, then after many trials between 4-6 inches, reduced to 5 inches), 4) distance between baffles (1 ft initially, then decreased to 5 inches between the end of a baffle to the next baffle, which decreased distance between baffle mouths to 6½ inches), and 5) ladder slope (10° initially, later 8° after slot velocity at 10% slope exceeded water velocity target).
Hydraulic conditions in the ASBS: water velocities were measured in the center of three contiguous alternating baffle slots in the straight ASBL (#13, 14, 15 upstream from the bottom of the ASBL, and at four stations at each baffle above the bottom (30 mm, 80 mm, 150 mm (6 inch or mid-depth), 200 mm; velocity at 270 mm was measured when available). Between these three baffles, we also characterized velocity vectors on a 1 inch2 grid of the entire wet area. Vectors were measured at ½ water depth using a 1 inch long yarn string on a vertical pole.
Results of R&D—slot velocities, flow vectors, eddy size.—The baffle design, baffle spacing, and baffle angle to the wall producing the target velocity in baffle slots in the straight section is shown in
In the 180° curve with a 4 ft radius on an 8% slope, eddys and velocities in baffle slots (two sample slots) were similar to eddys and velocities in the three monitored slots in the straight section. Baffle locations in the curve were configured using two measurements: a 5 inch slot width and 5 inches between the end of a baffle and the upstream baffle. These two measurements determined baffle length and baffle angle to the wall.
Results of R&D—fish tests.—After the target baffle slot velocity regime was obtained in the straight ASBL, wild fish were captured in July in local streams and introduced into the bottom of the ladder in the 4 ft long 0% slope fish introduction section and allowed to freely ascend the 13 ft long section at 8% slope. After the 180° and two 90° curve sections were added to the top of the straight ASBL (total lenth on 8% slope=25 ft) in October 2016, local riverine fish were captured and introduced into the fish introduction section, released, and observed for ascent and behavior. Fish behavior during ascent was monitored by personal observations, a PIT tag detection system (Oregon RFID) in June, and these methods plus an underwater video camera (GoPro camera) in October. Video observations found fish ascended a baffle slot throughout the water column, showing even the small fish used top to bottom slot velocities.
Many fish of several species in both tests ascended the ladder (Table 2). Tests found fish of several species with a moderate swimming could ascend the ASBL and did so quickly, indicating an easy ascent. Species and percent ascents of the top four species follow: Smallmouth Bass (80%), White Sucker (71%), Common Shiner 61%), and Largemouth Bass (50%). A remarkable result was the ascent of small Common Shiners only 3-4 inches long. We know of no other fish ladder in the USA that passes fish this small.
Tests with fish only lasted a maximum of 4 h and were only done in the day (typically, at 1100-1300 h). Thus, results indicated some fish from some species would ascend the ladder, and the ascent numbers are not an indication of the total number or percent of all test fish that would ascend given a longer time or nighttime.
Some fish species will only ascend a ladder at night or after a longer test time (Kynard et al. 2012); thus, results show only those fish that would almost immediately ascend. Ascent will be much greater with wild fish that voluntarily enter the ladder.
Test results show fish of diverse families, body types, and body lengths successfully ascended the ladder in either straight or straight+curve configurations (Table 2). The scale model ASBL successfully passed non-salmonid fish even though they were not migratory and were just attempting to escape the confines of the ladder.
In October 2016, we placed 8-9 inch long fish (one Brook Trout, one Common Shiner, and two White Suckers) at the top of the ladder and monitored their external condition after moving downstream past 33 baffle slots. Close examination of the fish's exterior after they reached the bottom of the ladder did not reveal bruising, missing scales, or external damage. We also commonly observed fish moving upstream, then downstream, then upstream to the top, observations showing that fish can safely move up- or downstream in the ASBL.
11. Description of the Invention
The invention is an alternating side-baffle fish ladder (ASBL). The following characterizes an ASBL of any dimension:
1) Side baffles that extend into the open channel alternating from side to side and vertically, top to bottom, along the length of the channel,
2) Baffle angle to their attachment wall=angled upstream at <90°, leaving a vertical slot opening between the end of each baffle and the opposite wall,
3) Flume dimensions: width, minimum=12 inches; maximum=none known; height, minimum=12 inches; maximum, none known; length=no maximum known.
4) Slope of ASBL: minimum=likely 3%; maximum, likely 12%;
5) Baffle slot opening width, baffle length, baffle spacing: inter-related factors of variable measurements determined for each ASBL to create a slow velocity in baffle slots depending on dimensions and slope.
These factors can be manipulated to create an ASBL for a wide range of ladder dimensions or site slopes that allow the ascent of a wide variety of fish species and sizes.
For example, these factors in the 1 ft wide×1 ft high scale model follow:
1) Rectangular flume dimensions (width and height)=12 inches wide×12 inches deep in a 13 ft straight ladder or 26 ft long straight+curve ladder, all at 8% slope.
2) Baffle placement across flume channel: alternate from left to right side of the ladder, from bottom to top of ladder, with open end of baffle facing upstream.
3) Baffle angle to attachment wall: 65° to the attachment wall in straight sections (
4) Baffle length and width of slot opening in straight section: length=8.25 inches, width of slot=5 inches.
5) Baffle spacing: from the end of each baffle at the slot opening to the upstream baffle is the same distance as the slot width (5 inches in scale model,
6) Ladder slope=8% (to obtain a mean slot velocity that allows small 4 inch long fish, like minnows and darters to ascend the ladder, as in the Eel R, IN.
Any design of an ASBL is dynamic depending on the selection of the two main factors: ladder width×height dimensions and slope. We have only measured factor values for a 12 inch ASBL on 10 and 8% slopes. We are presently building a 36 inch×12 inch scale hydraulic model to determine if we can expand the measurements found to be successful at creating moderate velocities in a 1 ft scale model and a 2 ft prototype (both on 8% slope) for scaling up to larger dimension ASBL (2.5 and 3 ft wide scale models for 5 and 6 ft wide prototypes). We suspect the larger dimension ASBLs may require a reduction in slope from 8% to maintain the target velocity range in baffle slots, but only R&D will show if this is needed.
Maximum width, height, and length of an ASBL are not known, but all could be much greater and potentially provide fish passage for fish with a moderate swimming ability. Minimum ladder dimension: width and height=1 ft×1 ft in the scale model seems a minimum size. Ladder height could be much higher depending on the variation in tail water level and the height of a ladder needed to operate during fish migration season. The ascent time of 30 min of small fish in the 70 ft long prototype, suggests an ASBL of several hundred feet long is possible.
The ASBL invention is different from full baffle configuration ladders, Denil or Steeppass fish ladders, because ASBL ladders have only side baffles that alternate from side to side throughout the length of the ladder. In an ASBL, side baffles create a moderate velocity zone in each baffle slot, with the fastest velocity in the slot being restricted to the outside wall, leaving moderate velocities in the remainder of the slot opening. The fast velocity zone along the outside wall continues downstream and around the downstream side of the large eddy to the lip of the downstream baffle (
Much of the water in an ASBL is circulating in the eddy between adjacent baffles with the remainder flowing downstream through a slot opening; thus, an ASBL ladder requires less water to operate than full baffle ladders. We estimate the 12 inch wide×12 high scale model required a Q of only 0.4 cfs.
The ASBL has two advantages over existing full baffle ladders for passing non-salmonids: a moderate velocity regime in baffle slots and a short distance between the upstream eddy and downstream eddy separated by the slot velocity, so fish swimming through a baffle slot in a ASBL ladder only have to swim a short distance to get to the upstream eddy (5-6 inches across the slot velocity to go from eddy to eddy in the 12 inch wide scale model or 10-12 inches in the 24 inch wide prototype). Thus, the small dimension ASBL seems perfect for passing small fish. Underwater video of small fish swimming through the slot velocity in the 2 ft wide prototype showed fish hesitated ascent at the downstream edge of the slot velocity, then quickly swam the 10-12 inches through the slot using burst swimming (video provided by Jerry Sweeten, Manchester University). Table 1 supports this observation of swimming ability.
The availability of our invention to agencies could enable them to envision river restoration plans not possible before. For example, the application of an ASBL for fish passage at river dams is obvious, but for the first time, agencies can pass small protected species or small migratory individuals of large species over natural barriers or dams. This may change riverine ecosystem restoration possibilities.
Maximum water velocity in mid-depth baffle slots is moderate (12-17 inches/sec for the 1-ft wide scale model (
12. Design of a 2 ft Wide×2 ft High Prototype ASBL
In the spring 2017, we designed a 2 ft wide×2 ft high prototype ASBL for Stockdale Dam, Eel River, Ind. The prototype was 2× the size of the scale model and design was done using the same six main factors used to design the 1 ft wide×1 ft high scale model.
BK-Riverfish,llc paid for ladder fabrication out of 3/16 plate steel, painting, and for shipping to Stockdale Dam. Providing the ladder was BK-Riverfish's part of a team effort to provide a fish ladder at the dam, which will not be removed because of the historic Stockdale Mill associated with the dam. Other partners in this project and their contribution were the US Fish & Wildlife Service, who provided funds for site engineering and site preparation and for monitoring fish passage, and for students from Manchester University, North Manchester, Ind., for assistance with installation led by Jerry Sweeten, Ph.D., Head of the Biology Department, Manchester University.
13. Installation of the Prototype at Stockdale Dam, Eel River, Ind.
The 2 ft wide×2 ft high×70 ft long prototype ASBL was assembled on site in only 10 hours (14-15 Aug. 2017;
14. Performance of the Prototype Passing Fish
After installation of the ladder, the Eel River discharge has been low creating about 5 inches of water depth at the top of the ladder for most of the days. We estimate 5 inches of water depth is needed for fish to ascend the ladder. On 3 days in September and October 2017, the ladder was opened for several hours during an increase in river height at the top of the ladder of about 5 inches. About 30 minutes after water began to flow into the ladder, thousands of fish were seen at the top of the ladder. Most were minnows (shiners), several species of fish from the family, Cyprinidae. Thus, fish were attracted to the ladder flow and ascended the 70 ft to the top of the ladder in about 30 minutes. With only 5 inches of water in the ladder, only small fish could physically ascend the ladder. Twelve species of fish were captured at the top of the ladder and identified: the largest was 8-9 inches long but most were ? 4 inches and some were only 3 inches long (Jerry Sweeten, PhD, Head of Biology Dept., Manchester University, N. Manchester, Ind.). These results show the ladder is performing as designed to pass small fish with a moderate swimming ability, like minnows.
Due to low river discharge in fall 2017, there was insufficient river discharge to operate the ladder and the PIT tag fish monitoring system is not yet operational. In spring, 2018, higher discharge levels will enable further evaluation of the prototype and allow us to characterize water velocity in the baffle slots.
It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.
The invention having been thus described, what is claimed as new and desire to secure by Letters Patent is:
This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 62/433,762 filed Dec. 13, 2016, which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62433762 | Dec 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16270442 | Feb 2019 | US |
| Child | 16553652 | US | |
| Parent | 16042906 | Jul 2018 | US |
| Child | 16270442 | US | |
| Parent | 15841158 | Dec 2017 | US |
| Child | 16042906 | US |
