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Low-head dams can cause dangerous currents near the downstream face of the structure. Fatalities at low-head dams with such currents, often referred to as “drowning machines,” are poorly documented. This technical note presents a new database of fatalities at low-head dams in the United States together with an interactive map and web-based user interface. The primary purpose of the system is to raise awareness, generate interest, and educate the general public and decision makers regarding these dangerous structures and the need for remediation. The database was designed as a normalized relational database of event dates, severity, location, reporter, and other circumstances. The open-access user interface allows the general public to browse fatal incidents by geographic location and to read incident circumstances. The system allows submission of new contributions from users including all metadata needed to characterize the incident. The database is structured to include documentation verifying each entry. The site can be viewed at http://dams.byu.edu/.
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INTRODUCING A LOW-HEAD DAM FATALITY DATABASE
AND INTERNET INFORMATION PORTAL
1
Edward W. Kern, Rollin H. Hotchkiss, and Daniel P. Ames
2
ABSTRACT: Low-head dams can cause dangerous currents near the downstream face of the structure. Fatalities
at low-head dams with such currents, often referred to as “drowning machines,” are poorly documented. This
technical note presents a new database of fatalities at low-head dams in the United States together with an
interactive map and web-based user interface. The primary purpose of the system is to raise awareness, gener-
ate interest, and educate the general public and decision makers regarding these dangerous structures and the
need for remediation. The database was designed as a normalized relational database of event dates, severity,
location, reporter, and other circumstances. The open-access user interface allows the general public to browse
fatal incidents by geographic location and to read incident circumstances. The system allows submission of new
contributions from users including all metadata needed to characterize the incident. The database is structured
to include documentation verifying each entry. The site can be viewed at http://dams.byu.edu/.
(KEY TERMS: low-head dams; rivers/streams; hydraulic structures; submerged hydraulic jump; data manage-
ment; public participation; hydraulic fatalities database.)
Kern, Edward W., Rollin H. Hotchkiss, and Daniel P. Ames, 2015. Introducing a Low-Head Dam Fatality Data-
base and Internet Information Portal. Journal of the American Water Resources Association (JAWRA) 1-7. DOI:
10.1111/jawr.12289
INTRODUCTION
Low-head dams are small drop structures in rivers,
streams, or channels. Low-head dams are constructed
to impound water, meter discharge, or maintain
stream slope. There is no universally accepted defini-
tion of a low-head dam. The U.S. Army Corps of Engi-
neers (USACE) National Inventory of Dams (NID) lists
dams that are either equal or exceed 25 feet (7.6 m)
in height or equal or exceed 50 acre-ft of storage
(61,700 m
3
) and exceed 6 ft (1.8 m) in height (USACE,
NID, http://geo.usace.army.mil/pgis/f?p=397:1:0::NO,
accessed December 31, 2013). Ostensibly, low-head
dams are smaller than either of these two categorical
definitions. While several databases and descriptions
of dams exist including NID and the World Register
of Dams (International Commission on Large Dams,
Registry of Dams, www.icold-cigb.org/GB/World_
register/world_register.asp, accessed December 31,
2013) there is no such compilation for low-head
dams. Listings in these databases are biased toward
large dams (Lehner et al., 2011). There are an
unknown, but large number of low-head dam structures
in the United States (U.S.).
Many low-head dams are dangerous due to a
hydraulic condition called the submerged hydraulic
jump (Rao and Rajaratnam, 1963; Leutheusser and
1
Paper No. JAWRA-14-0013-N of the Journal of the American Water Resources Association (JAWRA). Received January 9, 2014; accepted
January 5, 2015. ©2015 American Water Resources Association. Discussions are open until six months from print publication.
2
Water Resources Engineer in Training (Kern), Atkins North America, Phoenix, Arizona 85050; and Professor and Chair (Hotchkiss) and
Associate Professor (Ames), Department of Civil and Environmental Engineering, Brigham Young University, 368 Clyde Building, Provo,
Utah 84602 (E-Mail/Hotchkiss: rhh@byu.edu).
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION JAWRA1
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
AMERICAN WATER RESOURCES ASSOCIATION
Birk, 1991). Individuals who are familiar with this
phenomenon often refer to it as a “hydraulic” or
“drowning machine” (Borland-Coogan, 1980). A sub-
merged hydraulic jump forms when the downstream
depth, called the tailwater, rises to a level that
partially drowns out the supercritical flow that forms
at the base of the structure. A recirculating current
develops due to the momentum of the plunging nappe
and buoyant force of air entrained water downstream
of the structure. The surface velocity of the water
immediately downstream from the face of the struc-
ture is directed upstream. This upstream directed
surface velocity carries objects that have traversed
the dam back toward the plunging nappe. The
upstream directed surface velocity makes this condi-
tion dangerous. The line that separates upstream and
downstream surface velocities is called the boil. A
diagram and photo of an example submerged hydrau-
lic jump are shown in Figure 1.
The calm appearance of submerged hydraulic
jumps makes low-head dams deceptively dangerous;
rafters and swimmers may not perceive the dam as
a significant hazard (Tschantz and Wright, 2011).
Submerged hydraulic jumps can easily capsize boats,
rafts, kayaks, and canoes (Elverum and Smalley,
2012). If a swimmer gets caught in the current, they
are likely to be submerged by the force of the plung-
ing nappe, resurface upstream from the boil, and be
swept upstream to the plunging nappe to repeat the
process (Wright et al., 1995). The extent of air
entrainment makes swimming away from a sub-
merged hydraulic jump very difficult and the high
velocities are almost certainly faster than even a
strong swimmer could swim in ideal conditions
(Leutheusser and Fan, 2001). Despite the significant
hazards associated with low-head dams, the most
common rationale for their removal is environmental
(Pohl, 2002).
The purpose of this technical note is to introduce
a comprehensive database and educational website
that documents fatalities and low-head dams with
the intent to raise awareness and encourage remedi-
ation efforts. While this is the most comprehensive
database made available to date, it is not the first to
discuss public safety at low-head dams. Organiza-
tions such as the American Canoe Association com-
pile accident reports relating to recreational paddle
craft. The Association of State Dam Safety Officials
(ASDSO; http://damsafety.org/) provides links to
several papers and sites including the American
Whitewater Accident Database. State agencies often
produce yearly incident reports of boating accidents;
however, these reports often do not include recrea-
tional paddle craft. Fatal incidents involving swim-
mers are less likely to be documented than those
that involve watercraft. Well-funded media organiza-
tions may report on fatal incidents at low-head
dams. However, media coverage is less likely in
rural areas. The following section presents examples
of low-head dam fatalities represented in the data-
base.
Representative Low-Head Dam Fatalities
Drop Structure 2 in the Walnut Creek Flood Con-
trol Channel System (WCFCCS) in Concordia,
California has claimed eight lives since its construc-
tion (West Yost Associates, and Walnut Creek Flood
Control District, 2011). Fencing and signage restrict-
ing access to the channel has been present since the
structure’s completion in the early 1970s. Drop Struc-
ture 2 occurs just before a rectangular concrete
channel transitions to a trapezoidal earthen channel.
The structure is located in an urban area. The
incidents at WCFCCS Drop Structure 2 are as
follows:
1. February 2011, a pair of teenage boys tried to
raft the channel and drowned.
2. April 2010, a car crashed through the fencing
into the channel. A couple and their son were in
the vehicle at the time. They became captured at
the drop structure. The father and son were
drowned. The mother nearly drowned and a fire-
fighter was badly injured during the rescue.
3. 1991, a boy drowned while attempting to retrieve
a ball.
4. February 1973, three adults, aged 29-34 years
attempted to raft the channel. They were ejected
from the raft at Drop Structure 2. One person
was knocked unconscious and drowned.
Fortunately, members of the Flood Control
District’s maintenance crews were working at
FIGURE 1. Flow Paths in a Submerged Hydraulic Jump (top);
Toy Doll Trapped in a Submerged Jump (bottom).
JAWRA JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION2
KERN,HOTCHKISS,AND AMES
the structure when the incident occurred and
were able to rescue the other two rafters.
5. January 1973, two boys died when attempting to
retrieve a ball from the channel.
These descriptions contain information that may
be helpful when designing new drop structures or re-
mediating existing structures similar to WCFCCS
Drop Structure 2. Three of the eight victims were
intentionally rafting or paddling the channel. Assum-
ing that children attempting to retrieve balls were
not wearing personal flotation devices (PFDs), at
least five victims were not wearing PFDs. Six of the
fatalities were adolescents or children. At least five
fatalities occurred during winter. At least three peo-
ple have been saved by bystanders or rescue crews.
Despite restricted access, eight people lost their lives
at Drop Structure 2.
Many fatalities have occurred at the Dock Street
Dam in Harrisburg, Pennsylvania. The dam is pres-
ent to give the Susquehanna River sufficient depth
for recreational use. The crest length is more than
1 km. A news special aired in 1996 claims that 17
fatalities have occurred at the Dock Street Dam
between 1976 and 1996 (WGAL 8 News, 1996).
Boaters, paddlers, rafters, swimmers, and even a
snowmobiler have lost their lives at low-head dams.
Fatalities are not confined to recreational users.
Parents, siblings, and extended relatives have
drowned while attempting to save loved ones. Numer-
ous first responders and altruistic bystanders have
perished attempting to save strangers trapped in sub-
merged hydraulic jumps. At least five victims have
drowned while trying to save dogs. The sites where
fatalities occur are as diverse as the circumstances of
fatal incidents.
The remainder of this technical note introduces a
new database and associated web site and interactive
map, which have been developed to manage informa-
tion related to fatalities at low-head dam sites. The
database and web site allow immediate and open
access to all information available regarding incidents
at these structures. As in nearly every other field of
information science, the compiling and sharing of
data in a well-curated manner has the potential to
make important changes. It is hoped that the
database and interactive web site developed and
presented here can be a catalyst for promoting
retrofit, redesign, and remediation in existing low-
head dams ultimately reducing unintended loss of
life.
METHODS
Database Design and Development
A MySQL database was created to store fatality
and site information. The database is designed to be
as simple as possible while avoiding redundancy.
Simplicity allows the database to be maintained by
individuals with little MySQL training. Redundancy
is avoided to minimize the size of the database and
the possibility of duplicate entries. The database con-
sists of four tables: (1) Sites, (2) Incidents, (3) Reme-
diation, and (4) Verification as shown in Figure 2.
The Sites table contains information that pertains
only to an incident’s geographic location. The
Incidents table contains information that pertains
exclusively to a single fatal event. Information for
documents used to verify the location of sites and cir-
cumstances of incidents is stored in the Verification
table. The Verification table is not directly related to
the Sites table. A document stored in the Verification
table is related to an event in the Incidents table,
which is related to a location stored in the Sites table.
The Remediation table is not in use at this writing;
however, it can be used to track remediation mea-
FIGURE 2. Low-Head Dam Fatality Database Structure, Including Four Tables: Verification, Remediation, Sites, and Incidents.
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION JAWRA3
INTRODUCING A LOW-HEAD DAM FATALITY DATABASE AND INTERNET INFORMATION PORTAL
sures implemented at a site. Remediation measures
include, but are not limited to, posting signage,
restricting access, or retrofitting the structure.
The web site was created using HTML, CSS, Java-
Script, PHP, and MySQL. When a user views the
database, three PHP arrays are populated with the
information contained in the site, incident, and verifi-
cation tables. These arrays are used to create site
markers and ordered lists. The process for creating
the site markers and ordered lists is as follows: First,
the database is queried, the results of the query are
placed into arrays, and each array is sorted. An
appropriate title is displayed for each site. If a pic-
ture exists, it is placed below the title. The site_id
of each incident is checked against the current site; if
the site_id matches, the incident details are listed. If
an incident is related to a verification document, the
document details are displayed. The function loops
until all sites have been listed.
User Interface Design and Development
The low-head dam fatality web site was developed
with three primary user interface pages: (1) “About
Submerged Hydraulic Jumps,” (2) “Browse Incidents,”
and (3) “Report an Incident.” The “About Submerged
Hydraulic Jumps” page is the home page and can be
seen in Figure 3. It is for purposes of public educa-
tion. It contains a 24-min educational video created
by the authors and a short article summarizing the
information presented in the video.
The “Browse Incidents” page allows users to view
the interactive map and a list of all locations in the
U.S. where fatalities have occurred with their associ-
ated incidents. The interactive map can be seen in
Figure 4. The interactive map was built to allow indi-
viduals to browse fatal sites by geographic location.
Each site is represented by a marker at its
geographic location. When the cursor hovers over a
marker, the summary of information at the site is
displayed including the site name, total number of
fatalities, city, and state.
All fatal sites are listed below the map in alphabet-
ical order based on state, city (or county if not within
city limits), and site name. If a photo for the site has
been submitted it will be displayed below the site
title. The incidents at each site are listed below the
photo in descending order of date. The date, number
of fatalities, and a description of each incident are
displayed accompanied by links to the documents
verifying the information presented. If the user clicks
a marker on the map, the browser scrolls to the infor-
mation corresponding to that site. Ease of use is a
high priority. It is essential that each individual who
views the site can easily navigate to the information
they are seeking.
To ensure as many incidents as possible are
reported, the database is designed to allow submis-
sion of public contributions. The “Report an Incident”
page contains a user form used to submit unreported
fatality sites and incidents. If a form is not user
friendly, the user may become discouraged or disillu-
sioned and fail to submit beneficial information. The
user form is designed to encourage the user to
include as much relevant information as possible
without being restrictive or overwhelming.
System for Submission of New Incident Information
Information about the circumstances of each inci-
dent is vital for future studies. The description of
each incident will almost certainly include what the
victim was doing prior to becoming trapped at a
hydraulic structure. Other information that is useful
includes whether or not PFDs were worn, flow was
unusually high, the water was unusually cold, or
alcohol was a factor. Representative cases will be dis-
cussed in a later section. Incident-dependent data for
each site may include a vast array of information
that may be useful in future studies relating to reme-
diation measures at low-head dams. Useful informa-
tion for such studies may include site information
such as whether signs were posted or visible, fencing
was present, the site was otherwise restricted, or
portage was available.
A user may submit a new site and/or incident on
the “Report an Incident” page. When submitting a
new incident, an existing site must be selected or a
new site must be created. When creating a new site,
FIGURE 3. Home Page Linked from http://dams.byu.edu.
JAWRA JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION4
KERN,HOTCHKISS,AND AMES
the site name, latitude, longitude, city, county, and
state may be entered. The user has the option of
uploading an image of the site if one is available.
Most users will not know the latitude or longitude of
the location, and may not know the city or county. A
map is provided which allows users to zoom and click
on a geographic location. Clicking on the map will
automatically populate the latitude, longitude, city,
county, and state fields as shown in Figure 5. If
selecting a site that is already in the database, the
user may select the site from a drop down menu or
click the site marker on the map.
Once the site information is complete, the user
may enter information for the specific incident that
occurred, including the number of fatalities, day,
month, year, and description. The description is the
FIGURE 4. Interactive Map Showing Locations of Drownings at Low-Head Dams in the United States.
FIGURE 5. Interactive Map for Specifying Location of an Incident.
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION JAWRA5
INTRODUCING A LOW-HEAD DAM FATALITY DATABASE AND INTERNET INFORMATION PORTAL
field that will contain information regarding the
circumstances of the incident. If available,
documentation to verify the validity of the entry may
be included as a file or web link. The documentation
may be accompanied by a brief description which
may include who wrote the article and when it was
published. A verification document is not required.
The minimum information required to submit a
new site is the site name, latitude, longitude, state,
and either the city or county. The user must also
submit an incident when adding a new site. The
minimum requirements to submit an incident are the
number of fatalities, year, and a description. An inci-
dent may not be added unless it is assigned to either
a new or existing site. If an existing site is selected,
the fatalities that have been entered at that site are
displayed above the incident information user form;
the user is prompted to ensure that the incident they
intend to submit is not a duplicate entry. A Java-
Script function is used to ensure the information the
user intends to submit meets the minimum require-
ments. If the minimum requirements are not met, a
prompt advises the user what additional fields are
required.
Data Validation
All submissions recorded in the MySQL database
have met the minimum requirements for required
field completion. If a future submission is inaccurate,
vague, or inappropriate, it may be corrected or
removed by an administrator. The administrator can
search and edit the database at any time with a high
degree of flexibility using a MySQL database admin-
istration tool (e.g., phpMyAdmin). Each table in the
database has two fields related to validation. The
“validated” field contains a numerical value associ-
ated with the extent the entry has been validated. A
value of 1 indicates that the entry has been checked
for appropriate content and grammar. A value of 2
indicates that the accuracy of the content has been
verified. The “validated_by” field contains the name
of the administrator who most recently validated the
content of the entry. Data can be queried based on
the level of validation.
In addition to event metadata recorded by the data
contributor, the administrator also has access to the
submitters contact information and can request addi-
tional documentation as needed to fully verify the
event before it becomes a permanent addition to the
database. This is critical to avoid false reports and
contrived data. Generally, it is expected that the sub-
mitter will provide the web address of a verifiable
news report as documentation. In some cases, where
the news report is vague or lacking information, the
submitter may be asked to supply supplementary val-
idating information.
To prevent malicious software from exploiting the
database, a security field must be completed correctly
before submission is permitted. For additional secu-
rity, harmful characters are sanitized before entry
into the MySQL database. During the initial popula-
tion phase of the database, two incidents and sites
were submitted by visitors to the site. The database
creates a self-contained backup file once every seven
days. Each backup file is saved for two years prior to
deletion.
Initial Data and Database Sustainability
The developed database was initially loaded with
information and metadata regarding 430 fatalities at
222 low-head dam locations. The data for these inci-
dents was acquired through an extensive search of
public records databases throughout the U.S. Signifi-
cant contributions were made by Charlie Walbridge
of American Whitewater (http://www.americanwhite
water.org) and Dr. Bruce Tschantz. All data were
entered through the user form on the “Report an Inci-
dent” page. While this initial data entry effort
includes all well-known and widely reported low-head
dam fatalities, the database certainly does not
include all events. Rather the present dataset has
been loaded into the online system to provide a criti-
cal mass of information that can be added to as new
events are reported (both past and future). Such
events will be added by members of the database
development team, as well as through third-party
contributions via the web reporting system and using
the validation approach described previously.
The database and associated web interface will
continue to be maintained by research staff and
students at Brigham Young University. Because a
very small number of new incidents are reported each
year, the present method of manually checking each
incident before authorizing its inclusion in the data-
base is considered sustainable for long-term mainte-
nance of the database. In addition, to ensure the
viability of this database as a resource for decision
makers and managers in the future, the database will
be registered with the Dryad online data archiving
and indexing service (http://datadryad.org).
RESULTS
The resulting database and user interface can be
viewed at the following web URL: http://krcproject.
JAWRA JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION6
KERN,HOTCHKISS,AND AMES
groups.et.byu.net. Each of the user interface web
pages (“About Submerged Hydraulic Jumps,” “Browse
Incidents,” and “Report an Incident”) are visible to
the general public. The site is hosted through the Ira
Fulton College of Engineering and Technology at
Brigham Young University, Provo. There are no
usage restrictions. Links to the database can be found
on the ASDSO, American Whitewater, and Facebook
websites. As of September 14, 2014, the site has been
visited more than 13,500 times in its six months of
availability. During the period from August 17 to
September 13, 2014, for example, there were 1,041
views of “About Submerged Hydraulic Jumps” with
an average “stay” time of 6.41 min.
CONCLUSIONS
An extensive database of incidents at low-head
dams was created to save lives by garnering public
support for the remediation of dangerous structures
and making information about the incidents at these
structures readily available. As long as dangerous
low-head dams exist, there will be more tragic cases
and the database is destined to grow. The map and
database demonstrate the need for addressing stan-
dards to improve public safety at low-head dams. The
database is a catalyst to help engineers and lawmak-
ers gather the information necessary to determine
what remediation measures are required to make
dangerous structures safe.
LITERATURE CITED
Borland-Coogan Associates, 1980. “The Drowning Machine,” Film
Communications, video.
Elverum, K.A. and T. Smalley, 2012. “The Drowning Machine.”
Boat and Water Safety. Minnesota Department of Natural
Resources. http://files.dnr.state.mn.us/education_safety/safety/
boatwater/drowningmachine.pdf, accessed October 2013.
Hicks, B., 1996. “The Dangers at Dams,” WGAL 8 News, Harris-
burg, Pennsylvania. http://fishandboat.com/images/video/dams_
susq_v2/lowhead_wgal.html, accessed October 2013.
Lehner, B., C. Reidy Liermann, C. Revenga, C. Vorosmarty, B. Fek-
ete, P. Crouzet, P. Doll, M. Endejan, K. Frenken, J. Magome,
C. Nilsson, J.C. Robertson, R. Rodel, N. Sindorf, and D. Wisser,
2011. Global Reservoir and Dam Database, Version 1
(GRanDv1): Dams, Revision 01. NASA Socioeconomic Data and
Applications Center (SEDAC), Palisades, New York. http://
sedac.ciesin.columbia.edu/data/set/grand-v1-dams-rev01, accessed
December 2013.
Leutheusser, H.J. and W.M. Birk, 1991. Drownproofing of Low
Overflow Structures. Journal of Hydraulic Engineering, ASCE
177(2):205-213.
Leutheusser, H.J. and J.J. Fan, 2001. Backward Flow Velocities of
Submerged Hydraulic Jumps. Journal of Hydraulic Engineer-
ing, ASCE 127(6):514-517.
Pohl, M.M., 2002. Bringing Down Our Dams: Trends in American
Dam Removal Rationales. Journal of the American Water
Resources Association 38(6):1511-1519.
Rao, N.S. and N. Rajaratnam, 1963. The Submerged Hydraulic
Jump. Journal of the Hydraulics Division, ASCE 89(1):139-162.
Tschantz, B.A. and K.R. Wright, 2011. Hidden Dangers and Public
Safety at Low-Head Dams. Journal of Dam Safety, ASDSO 9(1):
8-17.
West Yost Associates, and Walnut Creek Flood Control District,
2011. Safety Evaluation for the Walnut Creek Channel and
Bancroft Drop Structure. http://ca-contracostacounty.civic
plus.com/index.aspx?NID=3076, accessed October 2013.
Wright, K.R., J.M. Kelly, and W.S. Allender, 1995. “Low-Head Dam
Hydraulic Turbulence Hazards” presented at the Western Regio-
nal Conference, Red Lodge, Montana, ASDSO, May 22-25.
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION JAWRA7
INTRODUCING A LOW-HEAD DAM FATALITY DATABASE AND INTERNET INFORMATION PORTAL
... Dam failure is not the only risk that outdated dams pose to human life and well-being. There have been 555 fatalities at 276 low-head dams throughout the United States since the 1950s (Kern et al. 2015), 19 of which occurred in Texas between 1995 and 2016 (Kern et al. 2015). Low-head dams generally result in fatalities when someone goes over top of the dam and becomes trapped in the submerged jump the dams create (Wright et al. 1995;Elverum and Smalley 2012;Kern et al. 2015). ...
... Dam failure is not the only risk that outdated dams pose to human life and well-being. There have been 555 fatalities at 276 low-head dams throughout the United States since the 1950s (Kern et al. 2015), 19 of which occurred in Texas between 1995 and 2016 (Kern et al. 2015). Low-head dams generally result in fatalities when someone goes over top of the dam and becomes trapped in the submerged jump the dams create (Wright et al. 1995;Elverum and Smalley 2012;Kern et al. 2015). ...
... There have been 555 fatalities at 276 low-head dams throughout the United States since the 1950s (Kern et al. 2015), 19 of which occurred in Texas between 1995 and 2016 (Kern et al. 2015). Low-head dams generally result in fatalities when someone goes over top of the dam and becomes trapped in the submerged jump the dams create (Wright et al. 1995;Elverum and Smalley 2012;Kern et al. 2015). River users are often unaware of the hazard these dams present (Tschantz and Wright 2011), and older structures may often go unregulated (Kern 2014). ...
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This study examines spatial and temporal trends in Texas dams, dam failures, and dam removals. Dams were examined from a statewide perspective and within 10 major river basins that collectively account for over 80% of all dams in the state. The state-scale and basin-scale analyses revealed similar patterns of dam occurrence, but there was greater variation in the patterns observed in both the purpose of dams and the timing for when most of the storage was created in each basin. Climate factors, mainly precipitation, influenced dam location. Population was not directly measured in this study but was an obvious influence on the spatial distribution of dams and their functions. While new dams are being built in Texas to secure future water supplies, documented dam incidents/failures have occurred in 15 of the 23 major river basins in Texas, with 328 total instances occurring since 1900. As the number of newly constructed dams and dam failures continue to grow across the state, so should the number of planned dam removals. Between 1983 and 2016, 50 dams were removed across the state. The purpose for the majority of removals was to eliminate liability concerns associated with aging dams. Future dam removals will likely continue to occur based on the number of older, smaller dams with potential liability concerns. As Texas’ dam infrastructure continues to age, dam removal is a practical management option for mitigating potential dam-related hazards and improving the connectivity and ecological function of river systems.
... Small dams can be modified to be safer for boaters (Schweiger et al., 2017) but there is no evidence that many dam owners actively make such modifications. Hotchkiss, Kern, and their colleagues at Brigham Young University assembled a GIS database entitled "Location of Killer Weirs" as part of an effort to put forth a "low-head dam fatality database" (Kern, Hotchkiss, & Ames, 2015, but this resource depends on incidents being reported from sites across the United States. ...
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Most of the United States' 2.5 million dams are not under the jurisdiction of any public agency. These small (under 6 ft [1.83 m] tall) nonjurisdictional dams, unregulated and not inventoried anywhere, endanger public safety and degrade riparian ecosystems. Their problems are increasing as structures age and storm events become more violent. Property owners can be held liable for problems at dams. Through several policy changes and legal actions, states can vastly improve the situation. States should consider expanded jurisdiction over small dams, a program of inventorying and mapping all dams in state waterways, owner education and outreach, and shared resources to allow for improved public safety and river restoration through best dam management or dam removal practices. This article is categorized under: • Human Water > Water Governance • Engineering Water > Planning Water • Water and Life > Stresses and Pressures on Ecosystems Abstract This dam in LakeCounty, Montana stands 6 ft (1.83 m) tall.
... Des accidents mortels affectant des pratiquants du cano?-kayak lors du franchissement des ouvrages ponctuent ?galement l'actualit? estivale des ?tats ?tudi?s ( Tschantz et Wright, 2011 ;Tschantz, 2014 ;Kern et al., 2015). Ainsi, la plupart des ?tats disposent d'une l?gislation pr?cise quant ? ...
... Dams and other flow-control structures can have dramatic effects on lotic habitat by altering water chemistry and flow (Baxter 1977), river geomorphology (Ligon et al. 1995), fish and macroinvertebrate communities (Lessard and Hayes 2003;Santucci et al. 2005;Tiemann et al. 2004) and can cause a reduction of gene flow among populations, leading to reduced genetic diversity and increased genetic differentiation (Wofford et al. 2005;McCraney et al. 2010). Low-head dams (small drop structures in rivers, streams or channels constructed to impound water, meter discharge, or maintain stream slope; Kern et al. 2015) and weirs have been shown to influence gene flow and genetic diversity in some darter species (e.g., Haponski et al. 2007;Beneteau et al. 2009;Sterling et al. 2012). Low head dams (hereafter dams) in the Comal and San Marcos rivers impound water for recreational use and are a potential source of habitat fragmentation for fountain darters. ...
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The endangered fountain darter Etheostoma fonticola is found only in the Comal and San Marcos rivers in the Guadalupe River basin in central Texas, USA. Comal River fountain darters were believed to be extirpated following a severe drought in the 1950s and were reintroduced in the early 1970s using 457 darters from the San Marcos River. In this study we used 23 microsatellite loci to describe and evaluate the genetic diversity, population structure and effective population size (N e) of fountain darters. We also evaluated the genetic effect of the Comal River reintroduction and the influence of low-head dams (dams) on dispersal in both rivers. Bayesian analysis of individual genotypes and Analysis of Molecular Variation supported two distinct populations concordant with the two rivers. Estimates of N e were much smaller (<10 %) than census size (N c) in both rivers but did not indicate the populations are at risk of an immediate and rapid loss of genetic diversity. Coalescent-based estimates of the genetically effective number of founders (Nf) for the Comal River averaged about 49 darters and, together with the indices of genetic diversity and the bottleneck test (heterozygosity excess) results, were consistent with a founder event following the reintroduction in the Comal River. Finally, our results regarding the influence of dams on fountain darter dispersal were equivocal and did not support a conclusion. We recommend this issue be examined further as part of the fountain darter recovery program.
... A growing community of professionals is investigating portfolios of infrastructure that meet infrastructure needs such hydropower and water supply, while also minimizing environmental damage (Ziv et al., 2012), meeting local subsistence fishing and agricultural needs (Richter et al., 2010), and addressing recreational safety (e.g. Kern et al., 2015). ...
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Water resources and transportation infrastructure such as dams and culverts provide countless socio-economic benefits; however, this infrastructure can also disconnect the movement of organisms, sediment, and water through river ecosystems. Trade-offs associated with these competing costs and benefits occur globally, with applications in barrier addition (e.g. dam and road construction), reengineering (e.g. culvert repair), and removal (e.g. dam removal and aging infrastructure). Barrier prioritization provides a unique opportunity to: (i) restore and reconnect potentially large habitat patches quickly and effectively and (ii) avoid impacts prior to occurrence in line with the mitigation hierarchy (i.e. avoid then minimize then mitigate). This paper synthesizes 46 watershed-scale barrier planning studies and presents a procedure to guide barrier prioritization associated with connectivity for aquatic organisms. We focus on practical issues informing prioritization studies such as available data sets, methods, techniques, and tools. We conclude with a discussion of emerging trends and issues in barrier prioritization and key opportunities for enhancing the body of knowledge. Copyright
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Dams, road crossings, and water withdrawals extensively fragment rivers, and watersheds often contain hundreds or thousands of barriers, some of which no longer meet societal purposes. Accordingly, both conservationists and infrastructure managers are faced with the challenge of prioritizing barriers for repair, replacement, or removal. Candidate projects have been prioritized with dozens of methods, which span a wide range of spatial scales, data and analytical requirements, mathematical complexity, and capacity to reconcile multiple perspectives and objectives. We briefly review barrier prioritization methods from the perspective of a policy maker or manager who must balance realities of stochastic opportunities, conflicting priorities, and risk of infrastructure failure. After outlining common motivations for barrier prioritization, we present a menu of techniques ranging from large‐scale, quantitative assessments to reactive, local response to failures. By clarifying the appropriate domain for each approach, this review informs the selection of prioritization methods for restoring riverine connectivity.
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This paper describes an experimental investigation of submerged hydraulic jumps forming downstream of overflow structures. Submergence happens when the hydrological tailwater depth in a channel exceeds the jump's subcritical sequent depth. It is a common occurrence, particularly with low overflow structures. The jump may produce a vortex having significant countercurrent free-surface velocities. This phenomenon is held responsible for frequent personal injury accidents of unwary recreationists, hence its appellation of "drowning machine." Experimental results, supported by analytical reasoning, are presented that quantify these dangerously high velocities for all hydraulic situations.
Article
Submergence of hydraulic jumps occurs frequently at low overflow structures, such as weirs and low-head dams. In these cases the jump degenerates into a rotating current that produces a strong upstream-directed surface velocity in an otherwise seemingly quiescent downstream pool. This vortex is commonly called the hydraulic by canoeists and water safety experts who fear and respect its potential to maim and kill, yet the phenomenon is virtually unknown in the hydraulic engineering literature. Using analysis and experimental evidence, the paper shows how the hydraulic may be eliminated by either increasing the height of the structure sufficiently to promote formation of a proper hydraulic jump, or by adopting the cascade concept of continuous energy dissipation on a baffled chute. In the former instance, the required height can easily become so great, however, that it may be deemed unacceptable. On the other hand, baffled-chute spillways are environmentally attractive, known to function well over a wide range of operating conditions, and completely independent of tailwater depth.
Article
Over 76,000 dams have been constructed on American rivers to provide services such as flood protection, water storage, hydroelectric power, and navigation. Although most dams continue to provide sufficient benefits to retain the structure, dam removal is becoming increasingly common. This study involved the construction of a dam removal database to analyze spatial and temporal trends in dam removal. The data included information on 417 cases of dismantled American dams, 153 with known rationales for removal. Database analysis indicated that the leading purposes for dismantling structures are safety concerns and interest in environmental restoration. There is substantial geographic variability in dam removal rationales, with California leading in razing dams for environmental purposes, and Wisconsin leading in economic and safety rationales. States with substantial removals tend to have programs that support and fund dam razing. Although removals for safety reasons have been increasing steadily in the past three decades, environmental removals made a rather dramatic and sudden entry into the dam removal arena in the 1990s. Analysis of spatial and temporal trends in dam razing are of particular significance given the likely increase in dam removals in the 21st Century.
The Drowning Machine
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Hidden Dangers and Public Safety at Low-Head Dams
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