TschantzWright_PublicSftyLowDams_JDS2011_1

8/22/2019 TschantzWright_PublicSftyLowDams_JDS2011_1

1/98 The JourNal of Dam Safe Ty | Volume 9 | ISSue 1 | 2011 ISSN 19 44 -9 83 6 -asscitin Stt D St oici

Bruce A. TschAnTz, Pe

KenneTh r. WrighT, Pe

ABSTRACT

Low-head dams, a.k .a. killer dams or drowning machines, oenpresent a saety hazard to the public because o their ability to trapvictims in a submerged hydraulic jump ormed just downstreamrom the dam. Most o these dams, normally producing vertical

water surace drops ranging rom one to a dozen eet, have beenconstructed across rivers and streams to raise the water level orthe purpose o improving municipal and industrial water supplies,

producing hydropower, and diverting irrigation water. Hundredswere built in the 1800s to power gristmills and small industries.

Many have allen into disrepair or been abandoned, posing dangerousconditions to the public. Kayakers, canoers, raers, swimmers, andother water users are oen unaware o the existence o hazards atlow-head dams, and sometimes end up getting trapped and drowningin the strong recirculating currents. Although hundreds have beenkilled over the last our decades, ew states regulate these dangerousstructures because o their small heights. Moreover, state dam saetyregulations ocus primarily on structural integrity and prevention oailure, but they do not generally consider public saety issues at oraround dams.

A recent study o accidents at these dams over the last our decadesreects a sobering reality o the problem rom a national hazard

perspective. Te hydraulic action below low-head dams is reviewedto show how it creates a water hazard, threatening public saety.Structural and non-structural measures to reduce drownings areexamined and a drowning case study is presented that the authorshave investigated.

I Introduction

Dam saety, or the saety o dams, has been in the public andtechnical topical oreront or almost our decades, since theBualo Creek tailings dam disaster and other notable dam ailuresincluding eton and Kelly Barnes in the 1970s. Te growing numbero government actions, organizations, articles, workshops andconerences about dam saety demonstrate this nations recognition

Hidden Dangers

and Public Safety atLow-head Dams

o the need or policies, standards, regulations, and institutions tomake dams saer and to reinorce a dam owners responsibility to

protect the public rom property damage and loss o lie in event ostructural ailure. Forty-nine states and all ederal agencies havingsome responsibility or dam saety have programs to regulate thedesign, construction, operation, inspection, and maintenance odams under their jurisdiction. Most states and ederal agencies haveemergency action requirements or warning the downstream publicin event o ailure. In addition, the National Dam Saety Program(NDSP) provides important support or the improvement o thestate dam saety programs that regulate most o the approximately84,000 dams in the United States included in the National Inventoryo Dams (USACE 2010).

What is missing in this vast array o programs to regulate thestructural saety o dams is a national, or coordinated, eort or

protecting the public at and around certain dams especially thosesmaller structures that are exempted because they all below the stateor ederal jurisdictional size categories. While there are thousands ounregulated dams, one notable class stands out: the low-head dam.Low-head dams are run-o-the-river, overow structures, usuallydened to be in the range o 3 to 5 meters in height, constructedacross rivers, with ow passing directly over the entire dam structureor the purpose o raising the water level to improve industrial and

municipal water supplies, protect utility crossings, and enhancerecreational opportunities. Low-head dams are also known as killerdams or drowning machines because o their capability to producedangerous currents, hydraulic orces, and other hazardous conditionsto anyone trapped immediately downstream rom the overowing

water. Te term drowning machine was rst used thirty years agoto describe this phenomenon in a video that underscored the dangersat these structures (Borland-Coogan, 1980).

Hundreds o these low-head dams were built across the U. S. duringthe 1800s to power gristmills and small industries. Hundreds morehave been constructed or irrigation and water supply diversion onrivers throughout the U.S. Te number o low-head dams in most


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states is unknown. Pennsylvania maintains aninventory o about 300 low-head dams and

Virginia estimates having between 50 and 100.In Ohio, over 200 low-head dams are reported,New Jersey has 120, Illinois has about 250, andIowa estimates having between 200 and 400(Allen, 2008). O 37 states that responded to a2004 national survey, 17 estimated having almost1700 low-head dams (schantz, 2004).

Hydraulic engineers are aware o the orcescreated by moving water and have a proessionalresponsibility to design sae structures to controland contain these orces. But, as Proessor HansLeutheusser (1988) pointed out twenty yearsago, a saely designed and executed hydraulicstructure does not, in itsel, render a water owharmless.

Across the country, many older dams thatno longer serve their original purposes havebeen abandoned and have allen into disrepair, creating dangerousconditions or the public. Unwary swimmers, kayakers, canoers,

boaters and anglers generally do not recognize this danger orunderstand the power o moving water at and below these dams.Some water users are actually attracted to the sporting thrill rom arushing cascade.

Figure 1 shows a dramatic June 30, 2009 rescue below a low-headdam on the Des Moines River, Des Moines, Iowa, where drowningshave occurred.

II Low-head Dam Hydraulics

Flow over a low-head dam can be characterized by the hydraulicso ow over a rectangular weir. Four distinct states o weir ow, asa unction o relative hydraulic jump depth (Y2) to tailwater depth(Y

), just downstream rom the dam, are presented in Figure 2.

Inspection o Figure 2 shows that an ideal hydraulic jump may ormimmediately downstream o a weir at the point o the overow nappeimpact when the local tailwater depth (Y) in a channel just matchesthe sequent depth (Y2) as the jump changes rom supercritical tosubcritical ow (Case B). Because the sequent jump depth dependsonly on the unit discharge over the weir and the plunging nappe

depth, but the tailwater depth depends on open channel owhydraulics, jumps may be pushed downstream or low tailwaterconditions (Y

2

> Y

), nally reaching a point where the sequent and

local tailwater depths match (Case A). For relatively high tailwaterconditions (Y > Y2) the jump may be orced upstream against the

weir, thus orming a mildly submerged jump (Case C). Te principleo momentum and specic orce would determine the location othe jump in cases A and B as described by Blanger (Chow, 1959).At ood conditions, or a combination o very high ows and hightailwater (Y >>Y2), the weir and overow nappe become ullyimmersed and the jump is wiped out, resulting in only undulatingsurace conditions (Case D).

When the jump is submerged (Case C), the smooth-looking nappeplunges vertically into a deceptively quiescent tailwater surace. Astrong underwater rotating current begins at the ront o the plunging

nappe. Te underwater vortex ormed by the submerged hydraulicjump is called a hydraulic by many kayakers and canoers. Case C,the most dangerous condition, is called a drowning machine becausethe rotating vortex can easily trap victims by orcing them downwardat the overow and keeping them circulating, rst by downstream-directed underwater current and then by the relentless reversedsurace countercurrent, until they become exhausted and drown.Because the plunging nappe entrains air, the rotating water becomesless dense and buoyancy is reduced, thus making it difcult or one toremain aoat. Reversed underwater currents that continuously pullobjects back toward the overall lower the chances o surviving.

Te other three jump conditions usually do not represent the danger

to people that Case C presents. For example, Case A occurs at lowows, accompanied by low velocities, low depths, and normally non-dangerous currents below a dam. Case B occurs or moderate owsthat produce optimum jumps, high energy dissipation, and rothy

water, but only localized turbulence. While Case D occurs or veryhigh ows, this condition is not dangerous because the dam andoverow nappe are completely submerged and the hydraulic jump,together with entrapping countercurrents, is eliminated.

A submerged hydraulic jump occurs when the local tailwater depth(Y) in the channel exceeds the jumps subcritical sequent depth(Y2), a condition that oen orms at low-head dam structures.Leutheusser and Fan (2001) described the submerged jump processFigure 1 Photo by Mary Chind, Copyright 2009, The Des Moines Register

and Tribune Company Reprinted with permission


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and reversed surace velocity characteristics o Case C based on resultsrom their model tests as ollows:

Once the jump is submerged, it becomes essentially a orced vortexeaturing a signicant upstream directed ree-surace velocity. Tevelocity is highest or mild submergence where, or all hydraulicconditions, its magnitude is approximately one-third o the supercriticalinow velocity o the corresponding unsubmerged jump. Tecountercurrent velocity decreases with increasing submergence ortailwater depth, until it suddenly drops to zero. When this happens,the submerged nappe, moving along the channel bottom, suddenlyips to the ree surace and, simultaneously, the vortex vanishes. Tephenomena o nappe ip and its counterpart o nappe op, inducedby a decrease o the tailwater depth, occur when the ratio o upstreamdepth (Ho) to tailwater depth (Y) is approximately 1.15 (Leutheusserand Fan 2001).

Leutheusser and Fan presented a dimensionless chart (Figure 3) orestimating the reversed surace velocity (Vs) as a unction o its ratioto the supercritical inow velocity, Vs/V1, and a submergence actorS = (Y - Y2)/Y2, as dened by Roa and Rajaratnam (1963). Figure3 shows that during each test, surace countercurrents (Vs) exist or arange o S rom zero to a value where a rising tailwater and increasing Sreach a critical point where the nappe ips ( ) to the ree surace, thejump is drowned out, and the vortex vanishes simultaneously. At thispoint, a dangerous countercurrent surace velocity ceases to exist. Onthe other hand, a decreasing tailwater depth and lower S orce the nappe

to op back (), to begin to cause dangerous countercurrent conditions.In other words, a dangerous condition will always exist or S-values lessthan the op () points or any Froude Number. Te small range o Sbetween ip and op is explained in terms o incomplete ventilationo the nappe when the tailwater decreases. Important conclusions andndings rom this work and other studies are as ollows:

In Figure 3, starting at about Vs/V1 = 0.25 where S = 0, the testcurves o dierent incoming Froude Numbers (F1) peak at aboutVs/V1 = 1/3 at S 0.25 to 0.30 and then drop gradually withincreasing tailwater and S to their respective ip and op points,which occur when the average tailwater depth (Y) to upstreamdepth (Ho) becomes approximately 1/1.15 or 87 percent.

Te longitudinal extent o the hydraulic zone, dened by thelength o the zone o reversed surace velocity and countercurrentrotation, measured downstream rom where the plunging nappemeets the tailwater, is between three and our weir or dam heights(Leutheusser and Birk,1991). Figure 4 shows this zone as CZ. Tedownstream end o the hydraulic zone is typically observed as atraverse band area across a channel called a boil (Figures 2C and4) where the rotating current rises to the surace, marking a splittingpoint between upstream and downstream currents.

Te dynamic impact orce o the alling nappe is estimated to bein the neighborhood o 1.5 times the weight o a mature person(Leutheusser, 1988). Tis orce can be estimated by applying theprinciple o impulse-momentum to alling water impacting a victimbody section

F = pAV2

where F = orce in pounds, = mass density o water(62.4/g), A = cross-sectional body area (2), and V = nappeoverow velocity (/sec) the point o impact.

Computed surace countercurrents (Vs) o up to 6 eet persecond are easily achieved under certain overow and tailwater

conditions. Such velocities are difcult to overcome or victimswho all into the countercurrent zone, and they challenge eventhe most highly trained swimmers to escape the pull toward theoverowing nappe.

Example

A simple example applied to ow over a typical low-head damillustrates the difculties that a victim aces in the water under Case Cconditions. Consider the situation shown in Figure 4.

Countercurrent surace velocity Vs can be estimated rom theprevious discussion. For example, assume that the height (P) o alow-head dam is 6 with water owing over the crest at a head (H) o

2 . Te tailwater depth or this ow is Y = 4.1 . Te overowingnappe produces an incoming supercritical ow depth (Y1) to orma hydraulic jump. Characteristics o the initial conditions o the

jump can be deduced rom experimental data and dimensionlesscurve solutions o the weir nappe energy equations developed byLeutheusser and Fan (2001) or H/P = 0.333 as ollows: IncomingFroude Number F1 = 4.75, initial depth Y1 = 0.50 , and initial

velocity V1 = 19.1 /sec. A orm o Blangers momentum equationrelates the initial and sequent depths, Y1 and Y2, to the incomingFroude Number F1 o a hydraulic jump as ollows:

Y2/Y1 = 1/2[(1 + 8F12)1/2 - 1]

For this example, the subcritical depth aer the jump is Y2 = 3.13 .

Note that the higher tailwater depth o 4.1 will thus orce the jumpupstream against the weir and cause it to be mildly submerged (CaseC). Te submergence ratio S = (4.1 - 3.13)/3.13 = 0.3 can be seenin Figure 3 to cause a maximum countercurrent velocity Vs/V1 ratioequal to about 0.31 or F1 = 4.75. Tus maximum surace velocitytoward the dam is Vs = V1 [Vs/V1] = 19.1(0.31) = 5.92 /sec, oralmost 6 /sec*.

Figure 3 Dimensionless

countercurrent plot

(Leutheusser and Fan, 2001)

*I the tailwater or this ow had risen to approximately 87 percent o the headwaterdepth Ho = 8 eet, or about 7 eet, S would increase to a critical ip point (approximately1.2 in Figure 3) where the jump would be completely drowned out and would no longer

produce dangerous countercurrents, as represented in Case D o Figure 2. It can also bedemonstrated or this example that tailwater depths within the range, 3.3



In this example the length o the countercurrent zone (CZ) shownin Figure 4 would be 3 to 4 dam heights long, or about 18 to 24 eet.Any oating body or object within this zone would be pulled backtoward the dam and its overow at about 6 /sec. Most struggling

victims caught in the middle o a wide channel or river would nd itdifcult or impossible to avoid being pulled back to the overow.

Reports o canoers and kayakers being pulled back to the allingnappe and capsizing are common. Stalled boaters, including rescuers,have allen victim to the same countercurrents and capsized upon

reaching the overow. Once struggling victims reach the nappe, theyexperience a dynamic orce alling over their head and torso areas,orcing them downward into the circulating current. In the aboveexample, i a victim is positioned under the alling nappe at a pointrepresented by V in Figure 4, the downward orce (F) rom the

penetrating water is estimated to be F = AV2 = (1.935)(.81)(15)2 =350 lbs, assuming a traverse surace area o 750 cm2 (0.81 2) or anaverage male body cross-section (Leutheusser, 1988) and an overow

velocity o 15 /sec at an overall distance o 3.9 , based on Rousesnappe prole measurements (Rouse, 1950). Tis downward orce isapproximately double the weight o most adult males and capable o

pushing the victim downward into the circulating current.

Where dams and waterways are not marked with warnings, boatersare oen unaware o, or do not appreciate, the potentially extremeorces and vortices at low-head dams and, or dierent reasons,unwittingly or purposeully glide over a seemingly innocuous overall,capsize in the alling water, get trapped in the hydraulic or keeper,and drown in the strong circulating currents. Te downstreamturbulence, accompanied by high aeration as evidenced by oamingor whitewater conditions, decreases the water density and thereorethe buoyancy o objects by as much as twenty to thirty percent,causing personal otation devices or liesavers to be less eectiveand making it hard or even a neutrally buoyant victim to stay aoat(Wright, 2008). Heavy logs and other debris trapped in the hydraulicmaintain a strong rotating pattern and create an additional hazard to

already helpless, panicking, quickly tiring and disoriented victims. Akayaker who drowned in 2000 was reported to have been strippedo his lie vest in the swirling waters below a low-head dam on theMusconetcong River in New Jersey (Meyer, 2000). emperature othe water is oen cool enough to add hypothermia to the mix o lie-threatening hazards. Adding to all o these is the dynamic orce othe water dropping over the dam that can exert hundreds o poundson a persons body.

In summary, the hydraulic orces in conjunction with the actorsdescribed above combine to create what has been described as anearly perect drowning machine.

III Case Study: Island Farm Weir Dam, Somerset

County, New Jersey

Island Farm Weir Dam was constructed across the Raritan River,as shown in Figure 5, in 1995 to raise the water level to improve

water supply draing during low ow conditions. Te RaritanRiver is classied by New Jersey as being suitable or recreationaluses, including boating. No warning signs had been installed on thelandings or boaters or other water users. On April 12, 1996, a canoer

who had paddled over the dam crest and through the hydraulic

was drowned in the recirculation ow o the reverse roller whileattempting to rescue a comrade who had gone over the dam in hiskayak and capsized. Te kayaker and another person in the canoeeventually made it out with the help o a sherman, but the victimsbody was never ound. Te river discharge on this date was estimatedto be about 2,000 cs over the 200-oot-long, 8-oot-high, ogee-shaped low-head dam.

Hydraulic analysis shows that or a tailwater depth o 7.6 eet anda head o 2.4 over the 8- high dam, the Froude Number, initialhydraulic jump depth, and incoming velocity o the submerged jump

were about 5.0, 0.6 , and 21 /sec, respectively. Tese conditionsare capable o producing a sequent jump depth o about 4 and

a tailwater submergence, S 0.9. For this degree o submergenceand surace water drop over the dam o only 2.8 eet, the reversedsurace velocity toward the dam was almost 5 /sec. Te length othe countercurrent velocity zone between the overowing nappe andboil point is estimated to have been between 25 and 35 eet, orapproximately 30 eet.

Figure 6 illustrates the dam and hydraulic characteristics at thetime o the drowning. Te strength o the countercurrent andoverpowering nappe orce, estimated at about 260 lbs, was apparentlyenough to drive the victim downward, entrap him, and ultimatelycause his death.

Figure 5 Original Island Farm Weir

Figure 4 Schematic showing example odrowning machine elements



A month aer the drowning incident, during similar ow conditions,a jet skier attempted to travel up the overow nappe o the dam, butell o the ski, was trapped, and had to be rescued with a line-gunrope. In October 1996, a local television station camera crew visitedthe Island Farm Weir dam to lm a story on high ooding duringa storm event. While they were lming, a canoer unexpectedly

paddled over the dam crest. He capsized against the nappe and ellinto the water, and, as the victim and his canoe bobbed up and down,the whole episode o the victims drowning was captured on tape or

viewers o the evening V newscast. Te victims body was ound aweek later.

Te Island Farm Weir was modied in 1998 aer our drownings andthree near-drownings in only three years ollowing its construction.Te successul retrot consisted o providing a series o steps on thedownstream ace (Figure 7) to dissipate energy and to eliminate theopportunity or a submerged jump and reverse roller to orm belowthe dam structure.

IV A National Problem

While accidents and drownings at low-head dams are reportedregularly in the local and national media, little statistical data isavailable to assess the ull national extent o the problem. MinnesotasBoat and Water Saety Section o the Department o NaturalResources reports 52 deaths and 50 injured or rescued people atlow-head dams in that state between 1974 and 2002 (Minn., 2003).In Illinois, the Fox River has a notoriously dangerous segment o 15dams in the 115-mile reach, just west o Chicago, between Wisconsinand its mouth at the Illinois River. At the 7-oot high Yorkville Dam(Figure 8), at least 12 people are reported to have drowned since it

was rebuilt in 1960. Drayton Dam on the RedRiver in Minnesota claimed 12 lives between1965 and 1995. On-going study by schantz odocumented news articles and other data sourcesrom 1970 through July 2010 reveals 155 injuryand/or death related incidents at low-head damsin 30 states. In these incidents, there have been atleast 48 injuries and 191 drowning deaths. Tesegures exclude 12 deaths reported at Drayton

Dam on the Red River since being constructedin 1964. One hundred eight, or 57%, o 191documented drowning deaths have occurred since2000, as indicated in Figure 9.

Documented inormation shows that o the 191drownings, use or non-use o personal otationdevices (PFDs) was known or only 56 victims.

However, use o PFDs didnt appear to make a dierence in theoutcome: 28 were known to have worn PFDs and 28 were knownto have not worn PFDs. Similarly, o 97 people who drowned aergoing over the dam, 18 were reported to have worn PFDs, while 19

were known to be without one. Reasons or the close split may bebecause PFDs oen get torn o in the hydraulic turmoil, buoyancy

is greatly reduced in highly aerated waters, and PFDs may becomesnagged on underwater objects.

Te distribution o the drownings and injuries rom low-head damaccidents across the country is shown in Figure 10.

Paddle sports and other water-based recreational activities havedramatically increased in popularity over the past twenty years.Te American Canoe Association reported that about 50 millionAmericans participated in canoeing, kayaking and other paddlesports in 2002, and that watercra recreation is expected to increase(Donahue and Earles, 2003). Paddler Magazine (May/June 2008)recently eatured an article, Te Drowning Machines, where severalexamples o drownings around the country are discussed. However, as

accidents continue to occur, it has become apparent that the specialhazards created by low-head dams to boaters and other water usershave allen through the cracks o attention between the state damsaety and the boating saety communities.

Figure 8 Yorkville Dam on the Fox River

Figure 7 Island Farm Weir stepped spillway modifcation



Most states do not regulate the design, operation or saety o low-head, or run-o-the-river, dams because o their small heights and/or impounding capacities and low hazard potential to downstream

property or lie in event o ailure. States tend to ocus primarilyon design, construction and operation o sae structures. Not

surprisingly, over the last 30 to 40 years since the Bualo Creekdisaster and the ailures o eton and occoa Falls dams, warrantedemphasis has been given by the dam saety community on

preventing dam ailures and protecting the public should ailureoccur. Considerable resources have been expended to inventory andclassiy dams, remediate or remove unsae dams, promote ownerresponsibility, develop and improve dam saety technology, postulatethe occurrence o ailures and promote emergency action plans, andgenerally regulate the structural saety o dams. However, thereare inherent residual hazards associated with sae dam and spillwaystructures that many design engineers tend to overlook. One paper

presented at the 1988 ASCE National Conerence on HydraulicEngineering emphasizes this oversight in its title: Dam Saety, Yes,

But What About Saety at Dams? (Leutheusser, 1988). In his paper,the author captures the irony o emphasis on structural saety at theexpense o other public saety needs:

Hydraulic engineers by their very calling are aware o theorces associated with the motion o water. Indeed, it is thecontainment and control o these orces which render their

proession so very challenging and satisying....[L]arge amounts o energy are released and dissipated, underully exposed conditions, in structurally sae weir-and-stilling-basin assemblies. While the environmental dangersassociated with these ow processes are well respected byhydraulic engineers, they are less so by the general public, and

serious accidents may be the consequence.All hydropower dams licensed by the FERC, including low-headtypes, are required to have a public saety plan that includesappropriate warning signs and other saety devices to protectswimmers, boaters and shermen. However, in a survey o statedam saety programs, only a handul (KY, LA, MA, PA, & WI)o 42 responding states indicated a requirement that some type o

warnings or buoys be placed near certain low-head dams (ASDSO,2000). Some states (IN, IA, MN, & OH) said they recommend orencourage owners to post signs near dams. Pennsylvania, ollowingseveral drownings at low-head dams, enacted its 1998 Act 91 (P.L.702) requiring notied owners o low-head, run-o-the-river dams to

warn the swimming, shing and boating public o the hazards posed

by such dams by marking upstream/downstream exclusion zones withwarning zone signs and other specied markers. Pennsylvanias damsaety program is responsible or inventory and notication activities,and the Fish and Boat Commission is responsible or establishingand enorcing sign and warning regulations at such dams. In Ohio,aer a rash o drownings, legislation was introduced in 2004 torequire owners o low-head dams to install warning signs and buoys.Te proposed bill ailed aer an ill-advised amendment, opposed bythe Ohio Department o Natural Resources (ODNR), was addedrequiring that gates be locked at public boat ramps during dangerous

water conditions.

In a 2004 survey o state boating law administrators, throughthe National Association o State Boating Law Administrators

(NASBLA), an organization o state ofcials responsible oradministering and/or enorcing state boating laws, only threestates (FL, PA, SC) were reported to have warning sign postingrequirements at low-head dams, with only Pennsylvania and SouthCarolina having sign posting laws to mark hazardous conditions and

prohibited access to dams (schantz, 2004).

More recently, Virginia enacted permissive leg islation (eectiveJanuary 2008), ollowing a series o drownings,allowingownerso low-head dams to use signs and buoys to warn the public o thehazards o swimming, shing, and boating activities near low-head dams. According to the Act, Any owner o a low-head dammay mark the areas above and below the dam and on the banks

immediately adjacent to the dam with signs and buoys o a designand content to warn the swimming, shing , and boating public o thehazards posed by the dam. Any owner o a low-head dam who marksa low-head dam in accordance with this subsection shall be deemedto have met the duty o care or warning the public o the hazards

posed by the dam. Any owner o a low-head dam who ails to mark alow-head dam in accordance with this subsection shall be presumednot to have met the duty o care or warning the public o the hazards

posed by the dam (Virginia, 2007). Te original bill was amendedshortly beore becoming law by substituting weaker language (mayor shall) thuspermittingrather than requiringowners to markareas around a low-head dam. However, duty o care remains animportant established orce.

Figure 10 State distribution o known drownings and

injuries at low-head dams 1970 - July 2010

States with death(s) (27)

States with injuries only (1)

Incidents - no deaths or injuries (2)

No documented or reported incidents (20)

Figure 9 Documented Drownings at Low-head Dams in

U S (1970 - July 2010)



swimmers and watercra users. Te Internet,print media, television, videotapes, CD/DVDs, workshops, and schools oer unlimitedopportunities or reaching and educating the

public about the dangers around dams. Tiseort presupposes the need to thoroughlyunderstand the extent o the problemidentiying potential hazards and evaluatingriskson a state-by-state basis in order to put

the issue into perspective and to prioritize theneeds. Specic target audiences and potentialorganizations or promoting education andawareness need to be identied. Materialssuch as boating saety inormation and training

videos, CDs, brochures such as distributed by the MinnesotaDNR and the Miami Conservancy District (2011), mapsshowing low-head dams, public service announcements, on-linecourses, and websites need to be inventoried to determine

what is already available, what works, and what remains to bedeveloped in order to promoteeective educational programs.

2. Warning markers and eective

legislation and regulation atthe state level requiring damowners to install appropriate

warning signs and buoys, escape,portage, saety and other devicesat low-head dams. It is essential,rom a public saety standpoint,

In April 2008, Iowa enacted a low-head dam public hazard programor establishing a low-head dam public saety program. Te

program includes compiling an inventory o low-head dams orpurposes o publicizing hazards through maps and warning signage,recommending design templates to reduce drowning, developingcriteria or removal, and establishing a prioritizing system or undingremoval and hazard reductions (Iowa, 2008).

Clearly, the problem o drownings at low-head dams in the U.S. iswidespread and growing. More state regulatory programs are needed

to reduce the danger to the public.

V Proposed Measures to Reduce Drownings

As the number o people attracted to water recreational opportunitiesincreases, water-related accidents and deaths are inevitable, butengineers, state and ederal ofcials, boating saety organizations, andrecreational watercra organizations need to work together to reduceor eliminate the environmental hazards at low-head dams. A ve-stepapproach is proposed to reduce the risk to the public rom dangerousconditions at low-head dams:

1. Public awareness programs that promotesaety education and cognizance o the potential

dangers at low-head dams. Tese programs wouldrequire the cooperation o several communities:the boating public, including national canoeing,raing, kayaking and boating organizations;local clubs; design engineers; dam owners; publicofcials, including legislators and local, state andederal regulators; and boating saety and boatinglaw administrator organizations to better educate

Minn.Dept.ofNat.Resources(2008)

Pa.Dept.ofEnv.Prot.

MiamiConservancyDistrict

(2011)



that dams be marked to warn the public o their existenceand potential hazard, especially as a result o changing owconditions (Schweiger, 2006). All low-head dams should beinventoried and periodically monitored and inspected or saetycompliance. Hazardous dams with a history o accidents shouldbe identied and receive priority or warning and protecting the

public. Existing state legislation and regulations related to publicsaety requirements at low-head dams should be researched,and model legislation and regulations should be developed.

FERC guidelines and standards or saety signage, public saety,and warning systems at hydropower projects have provided atemplate or many other ederal agencies to develop their ownguidelines (FERC, 1992, 2001).

3. Structural modifcation o low-head dams. Te physical hazardto boaters, shermen, and swimmers around and below low-head dams needs to be reduced or eliminated wherever practical,given the reality o technical, legal, environmental, and nancialconstraints. A technical manual should be developed or designengineers to stimulate a range o practical alternatives such asull or partial dam removal; use o engineered structures likestepped spillways, gabion baskets, at slopes, cascading pools, ordumped rock to dissipate energy and eliminate the hydraulic;

chutes to accommodate boaters; and portage ways or boatersto saely bypass a dam. Ohios dam saety program (Ohio, 2011)and the Heinz Center (2002) have developed excellent low-headdam removal rameworks or decision making and to discussissues to consider prior to removing dams.

4. Rescue trainingprograms to help state and local water rescue

proessionals understand and respond to the special hazardscreated at low-head dams. Many rescue personnel have diedattempting to save others trapped inside a reversed currentbelow low-head dams. Te Boat and Water Section o theMinnesota Department o Natural Resources has a study guideand three training videos or Minnesota-based organizationsthat review conditions and rescue techniques at ast-water andlow-head dams, including one called Te Drowning Machine(Minnesota DNR, 1997). ASDSO, NASBLA, ederal agencies,and the various national watercra saety organizations shouldorm a core team to coordinate the development o a standardstate training program, perhaps modeled aer Minnesotas

program.

5. Develop comprehensive national guidelines or public saetyat dams or identiying potential hazards and evaluating risks;changing operating practices; installing standardized warningsystems, signage and saety controls; developing site-specic

public saety plans and inspection and maintenance programs;and developing a continual review and improvement processor dam owners and operators, design engineers, and otherstakeholders. Te guidelines would also include some o theelements discussed above in steps 1 - 4.

Te Canadian Dam Association (CDA) has draed a manual,Guideline or Public Saety Around Dams and supportingtechnical bulletin, Public Saety Signage Around Dams. (CDA,2009). Te CDA recognizes that an important aspect o dam saetymanagement is protecting the public rom hazards associated withthe operations o dams throughout their liecycle, particularly whenspilling water or under rapidly changing ow conditions during

power generation. Such thinking goes beyond the traditionalinterpretation o dam saety as being primarily concerned with

protecting the public rom catastrophic ailure triggered by extremeevents. Te guideline recognizes that dam acilities may createdangerous hydraulic conditionseven or small unregulated low-head dams. Te guideline outlines a comprehensive public saety

plan or reducing or eliminating hazards at dams. Te plan includes asystematic management approach or identiying hazards associated

with the site, assessing the degree o public interaction arounddams, establishing dam owner accountability, identiying measuresor mitigating the hazard, installing physical barriers and warningsystems, educating the public o the hazard, providing or emergencyresponse, and reporting incidents. Te guideline dra, currentlyundergoing discussion, presents an eective approach and template tothe US dam saety community in developing responsible public saety

programs around dams.

Te US dam saety community would do well to ollow Canadasexample in developing comprehensive guidelines and standards or

public saety to minimize the public risk around damsespeciallyor the unique low-head type. As it is now, hundreds and possiblythousands o low-head dams in this country expose water users todangerous hydraulic conditions. As water recreation increases, along-term eort by dam owners to structurally reduce or eliminatethe hazard should be complemented by immediate measures byowners or warning the public and by state-wide programs orraising public awareness. States, acting through cooperation amongall aected agencies involved with dam saety, boating saety, andrecreation, need to inventory their low-head dams, assess their hazardand begin to take action to save lives rom this hidden menace byadopting eective legislation and regulation.

Reerences Cited:

Allen, David (Dam Saety Program Manager) and Nate Hoogeveen(Water rails Coordinator), telephone conversations on Iowa low-headdam inventories and estimates, Iowa Dept. o Natural Resources, DesMoines, February 28, 2008.

ASDSO, Annual Survey o State Dam Saety Programs response toquestion, Does your state require posting o warning or barriers nearlow-head dams? Please describe or provide citation, September 2000.

Borland-Coogan, Filmspace Productions, Te Drowning Machine(video), 1980.

Minn DNR Fast Water Rescue School demonstration

Photo by Tim Smalley, Minn. DNR.


9/9The JourNal of Dam SafeTy | Volume 9 | ISSue 1 | 2011 17ISSN 1944-9836 - asscitin Stt D St oicis

Canadian Dam Association (CDA), Guideline or Public Saety AroundDams (DRAF), scheduled or completion in mid-2009.

Chow, Ven e., Open Channel Hydraulics, McGraw-Hill, Inc., Chapters3 & 15, 1959.

Donahue, M. G. and . A. Earles,Recreational Use Considerations inPlanning and Permitting Low Head Dams, Proceedings, Dam Saety2003, Annual Conerence Proceedings (CD), Minneapolis, MN, Sept.7-10, 2003, Association o State Dam Saety Ofcials (ASDSO), 7 pp.

Federal Energy Regulatory Commission (FERC), Guidelines or PublicSaety at Hydropower Projects, Div. o Dam Saety and Inspections,March 1992, 21 pp. + 6 appdcs.

Federal Energy Regulatory Commission (FERC), Saety Signage atHydropower Projects, Div. o Dam Saety and Inspections, October2001, 43 pp.

Heinz Center or Science, Economics and the Environment,DamRemoal, Science and Decision-making, 2002, 221 pp.

Iowa Senate File 2380, Act orEstablishing a Low Head Dam PublicHazard Program, legislation signed by Gov. Culver, April 11, 2008.

Leutheusser, H. J., and J. J. Fan,Backward Flow Velocities o Submerged

Hydraulic Jumps, ASCE, J. or Hydraulic Engr., June 2001, pp. 514-17.Leutheusser, H. J.,Dam Saety Yes, But What About Saety at Dams?,Proceedings, 1988 National Conerence, ASCE, Hyd. Div., ColoradoSprings, CO, August 8-12, 1988, pp, 1091-96.

Meyer, Z., Suburban Philadelphia Inquirer article,Missing Bucks Man isFeared Dead in Kayak Accident, August 20, 2000.

Miami Conservancy District, Te Great Miami Rier - Play It Sae,Boating Map & Guide; brochure, videos or saety at low-head dams,2011 (see low dams at www.miamiconservancy.org).

Minnesota Dept. o Natural Resources (DNR), Boat and Water SaetySection, Boat & Water Saety Brochure: Te Drowning Machine (KimElverum, im Smalley,2008); 3 videos: Water Rescue (#387), Water:the imeless Compound (#150), and Te Drowning Machine (#172), St.Paul.

Minnesota Department o Natural Resources, Boat and Water SaetySection, 1974-2002 Dam-Related Accidents, Spreadsheet data table o63 accidents provided to author, 3 pages, 2003.

Ohio Dept. o Natural Resources, Division o Water, Low Head DamInventory and Removal Program, Framework website (2011): http://www.dnr.state.oh.us/water/tabid/3357/Deault.aspx

Paddler Magazine, Te Drowning Machines, article by Christian Knight,May/June 2008. pp. 46-53.

Rouse, J., Editor,Engineering Hydraulics, Chapter VIII, Section 10,

1950.

Schweiger, P. and M. Morrison, Saving Lives at Killer Dams, ImproingPublic Saety at Low Head Dams, Annual ASDSO Conerence DamSaety 2006 Proceedings, Boston, Mass, Sept. 10-14, 2006.

schantz, B. A., Te Hazards o Low-Head Dams: (How) Can WeMake Tem Saer?, Annual Conerence Proceedings (Abstract),National Association o State Boating Law Administrators (NASBLA),Chattanooga, N, Sept. 11-15, 2004, p. 18.

U. S. Army Corps o Engineers, 2009 National Inventory o Dams(NID), EP 360-1-23, July 2010.

Bruce A. schantz, PE, is Proessor Emeritus in theUniversity o ennessees Civil and EnvironmentalEngineering Department, where he taught water resourcesengineering or 37 years. Dr. schantz is currently a seniorresearch associate or the ennessee Water ResourcesResearch Center and a consulting engineer in Knoxville. Heestablished FEMAs Ofce o Federal Dam Saety where heserved as the rst Chie o Federal Dam Saety in 1980. Dr.schantz has made many presentations and written severalarticles on the hydraulics o and public saety at low headdams. He is an Honorary Member in ASDSO, an ASCEFellow, and is a registered engineer in ennessee, Ohio,

Virginia and Alabama.

Kenneth R. Wright, PE, is chie engineer and ounder oWright Water Engineers, Inc., Denver, Colorado. Mr. Wrightis a member o ASDSO, a Distinguished Member o ASCE

and has authored several papers on low-head dams. Mr.Wright is a registered engineer in 14 states and a Diplomate oWater Resources Engineering through the American Academyo Water Resources Engineers. He received the Order o Meritor Distinguished Service to the Republic o Peru, and severalacademic awards or paleohydrologic research at Mesa VerdeNational Park and at the Peruvian archaeological sites oMachu Picchu, ipon and Moray.

Bruce A Tschantz, PEPss eitsunivsit Tnnss1508 mting hs rdKnxvi, TN 37931

865/5315624

[email protected]

Kenneth R Wright, PECfo nd Ci enginWigt Wt engins2490 Wst 26t avn,Sit 100a\Dnv, Co 80211

303/4801700

[email protected]

Virginia Acts o Assembly, 2007 Session, Chapter 664, An Act to

amend and reenact 29.1-509 o the Code o Virginia,Duty o care andliability or damages o landowners to hunters, fshermen, sightseers, etc.,relating to Low-head Dams, Eective Jan. 1, 2008, Approved and signedby Gov. Kaine, March 20, 2007.

Wright, K. R., . A. Earles and J.M. Kelly,Public Saety at Low-HeadDams, Proceedings, Dam Saety 2003, Annual Conerence ProceedingsMinneapolis, MN, Sept. 7-10, 2003, Association o State Dam SaetyOfcials (ASDSO), 14 pp.

Wright, K. R., Earles, . A. and B. A. schantz, telephone discussion,March 3, 2008.

Documents

TschantzWright_PublicSftyLowDams_JDS2011_1