facts about dams

Facts about DAMS.

  • Facts about dams.
  • Why do we need dams.
  • How dams are classified.
  • The dangers associated with dams.
  • How to determine your RISK LEVEL if you live near one.

Dams are very important and necessary structures. 

  • Some facts about dams.
  • Dams are used to redirect river flows in order to use the water in other areas that would be more beneficial. An example would be for irrigation systems for farms.
  • Dams are used to create reservoirs for water supplies for cities.
  • An important function of a Dam is to control flooding.
  • Used in the generation of hydro-electricity.
  • To control river levels to help navigation of boats and barges.

There are 3 types of Dam Structures:  


  • Embankment Dams are constructed out of earth and rock and are the most common type of dam, making up approximately 80% of the total of all dams. Embankment dams can be massive in size.
  • Gravity Dams are straight concrete walled dams that are used in narrow valley areas.
  • Arch Dams are similar to Gravity Dams but are built with an arch design. This arch design enables the dam to hold back more water with less concrete.  Hoover Dam would be an example of an Arch Dam.

The Dangers associated with Dams.


  • Dangers with Dams.

    Dangers with Dams.

    Dams, like any other structure, need to be maintained due to wear and tear. There are many dams that are in need of repair.

  • Dams are particularly susceptible to earthquakes.  Small defects in a Dam’s structure can be quickly amplified with even a small earthquake.  Some dams have even been built either very close to or on top of fault lines.
  • Due to one of the important functions of a dam – to create a reservoir to store a water supply for a city – the dams are usually placed where large populationsare located.
  • Security issues associated with a dam.  If a dam falls into the hands or a terrorist group, it could turn real quick into a major disaster.  This potential danger recently happened with the Mosul Dam in Iraq in August 2014.  If the terrorist group did cause the dam to fail, loss of life estimates were calculated to be between 500,000 and 1,000,000+ .  http://www.zerohedge.com/news/2014-08-26/worlds-most-dangerous-dams
  • Dams are considered “installations containing dangerous forces“ under International Humanitarian Law due to the massive impact of a possible destruction on the civilian population and the environment. http://en.wikipedia.org/wiki/Dam_failure
  • The American Society of Civil Engineers gave the dams in the U.S a grade of “D” in 2013.  http://www.infrastructurereportcard.org/a/#p/dams/overview


Notable Dam Failures in History:


  • The deadliest dam failure was as recent as 1975, the Banqiao and Shimantan Dams, China. This dam failure was caused by extreme rainfall and killed 171,000 and 11 million people lost their homes.
  • The Machchu-2 Dam, India in 1979. This dam also failed due to heavy rain.  This failure caused an estimated 5,000 to 10,000 deaths.
  • South Fork Dam, Johnstown, PA, USA 1889. Failure was due to extreme rains and poor maintenance and cost 2,290 people their lives.
  • South Carolina during the month of October 2015 had several dams fail due to the historic amounts of rain they received during the month.   Read more details in our blog by clicking on the blue button.  Blog Post on South Carolina’s Dam Failures.


Here is an excellent video from the Documentary Channel that discusses the Dangers associated with Dams.

 The YouTube Link is: https://youtu.be/wlKZ8Ubx2rg


How to determine Your Risk Level for Dam Failure in Your Area.


There is Good News and Bad News when it comes to determining your risk for a dam failure. 


Let me start with the Good News First:  

There is some very good information available for learning about the dangers when living by a dam.  The best one I came across is offered by FEMA “Living Near Dams”.  Note the quote that appears on page #8 of the brochure: “Dams failures are low probability but high consequences.  But they typically happen somewhere in the U.S. every year.”  You can download the brochure by clicking on this button:  FEMA: Living With Dams – Know Your Risks http://www.livingneardams.org/brochure/files/assets/downloads/publication.pdf

The Association of State Dam Safety Officials has a good website that has a map of the United States.  You click on the state that you live in (or researching) and it will give you a map of the state with little bullets on it showing the locations of the dams in that state. The site also gives you the number of: High Hazard, Significant Hazard, and Low Hazard Dams located in the state.  Click this button to get this information.    Association of State Dam Safety Officials http://www.damsafety.org/community/states/?p=2827bd14-b6e3-49a9-a465-b2a3531afe5c

Note: High, Significant and Low Hazard Dams does not refer to the structural condition of, or the possibility that these dams may, or may not fail. What these hazard levels refer to are “IF” THE DAM FAILS then the (potential) damage that may occur downstream from the Dam, the “Dam Breach Impact Area”.

Now for the Bad News:

After literally spending days researching information on my local dams to assess the risks for my location, I noticed I kept running into walls and road blocks.

It is very difficult to get information regarding the “Structural Integrity and/or Potential Risk of Dam Failure” for a specific dam.  This information is kept for every dam.  I felt that this is very important information to have for anyone living near (downstream) a dam.

I found this extremely strange since there is so much information available about dams.  Ranging from Good: like the FEMA Booklet listed above about “Living Near Dams”.  To the Bad news about dams: The American Society of Civil Engineers giving the Dams located in the U.S a grade of “D”.

During my research, I came across two general reasons that attempted to explain this blockage of information.

The first theory is related to security issues and terrorism.

The government wants to control who this information goes out to. Now initially, I thought this theory made perfect sense, until I kept digging deeper into this topic.

There is a master database that catalogs the information for all of the dams in the United States that are: 25 feet in height or higher and exceed 15-acres of storage or is 6 feet or higher and exceeds 50-acres of water storage. This database is called the “National Inventory of Dams” [a.k.a. The NID] and is under the jurisdiction of the U.S. Army Corp of Engineers.

Now anyone can go to their website (http://geo.usace.army.mil/pgis/f?p=397:1:0) and get general information about the number of dams located in a particular state, the total numbers of dams in the state by potential hazard classification  (again: this is a classification system of potential hazard to the downstream area  from a dam if it fails – not the risk of the Dam itself failing) – even a map of the state you are researching will little dots showing all of the general location and distribution of dams in the state.  But you can’t get information regarding the “Risk Factor of Failure” about a specific dam.

They will only release this information to other “governmental agencies” or approved parties.

I thought that was a bit odd;  they are willing to tell you how many Dams are in the state that have High and Significant Hazard Potential for potential downstream damage – but they don’t tell you which ones are in poor condition and are at risk of falling apart.

I emailed them to ask how I, and the subscribers to this website, could get specific information about a dam that could potentially have a major impact on our property and possibly even on our family’s life.

They responded back within an hour with a very polite email.  Basically thanking me for the inquiry and how the system works to classify potential downstream failure.  But did not, and would not answer, the question about the potential of “Failure” for a specific dam.

This is how they ended their response to me:  “Because of security concerns, this information is restricted.  However, if you contact the state dam safety office that regulates a particular dam, they will normally provide itsdownstream hazard potential classification.  A security concern is the aggregation of dam information so most dam regulating agencies (state and federal) will provide this information on a dam by dam basis.  A good list of state dam safety points of contact can be found on the Association of State Dam Safety Officials web site,  http://www.damsafety.org, go to the map.  There are also additional state reports available from the same web site.”

This still does not answer the question about the “Structural Integrity, Condition or the Risk of Failure” for a specific dam in my area.  It only answers the “downstream hazard potential” – and does not address the dam itself.

The second theory is that the government is holding back this information in order to:

  • To cover up their insufficient dam safety measures.
  • Avoid depressing real-estate values in the areas of  dangerous dams.
  • Prevent the local citizens from demanding to spend the money (that is not available) to repair defective dams.

The Society of Environmental Journalist” reported back in October 2013 in an article titled, “Dam Secrecy Endangers Lives, Property of US Public in Many States”, that they too were blocked from access to this vital information.  Here are some excerpts from this article: http://www.sej.org/library/disasters/dam-secrecy-endangers-lives-property-us-public-many-states

  • “Tens of thousands of U.S. citizens are at risk from potential dam disasters, yet state and federal agencies hold to a policy that amounts to “out of sight, out of mind.”
  • The biggest danger, apparently, is that the public might find out about the dangers, and criticize insufficient dam safety measures, inconvenience private dam owners, depress real estate values, or demand public spending that is politically painful for those in office. Their chosen solution: whip up fear of terrorism, impose secrecy, and do very little.
  • If you live downstream of a dam whose failure might kill you or destroy your home, the U.S. Army Corps of Engineers (a lead agency on dam safety) will not let you know that fact. Even though the information is already in the public domain by other means, the Corps has blacked out such hazard ratings from its National Inventory of Dams. Many state agencies also withhold the information.”

All I can say is BIZZARO!


Well – Practical Disaster Planning Will Not Give Up!  We will find A way for you to determine your Risk Level of Dams for your location.  This is just too important of a topic to turn our backs on.  

So let’s start Assigning ourselves a Risk for Dam Failure:


NOTE: We have included a short video on how to do a Risk Analysis for Dams at the end of this section. The video may make it easier to follow the directions.


There are two components you will need to determine your Risk for a Dam failure:

  • Where are the Dams in relationship to your area (or location you are researching)?
  • What is the Hazard Classification of the Dams that are in your area (or location you are researching)?


There are a few ways to locate most of the dams in your area.


  • If you are familiar with the area – you may already know this simply by growing up in the area or driving around the area.
  • You may have luck using Google, Yahoo or Bing searches for Dams in your city, town, county, state.
  • The search I had the best luck with was with lat-long.com. This website is a good for finding many different features located in the United States.   It will at least narrow the list of dams down to the county you are researching.   You will then need to determine which ones are located nearest to you and have the potential to impact your location.

°  Click on the button for the website.  [  button link=”Lat-Long.com”] Lat-Long.com[/button]    Lat-Long.com

°  At the top of the page select the state (it will be a drop down menu in the Green Box at the top) you are researching.

°  The list of dams can be quite long. So enter the County of the Sate you are researching.  If you are not sure of the county your location search is located in;  Simply Google the Town or City and you can find the County quickly and easily.

°  Under the Feature Option – Scroll down and choose Dams.

°  Click on the box “Lat-Long Search” just to the right of the Feature Box.

°  You will be given a list of dams located in the State and County you are researching.

How to determine the Hazard Classification of the Dam(s) that are located in your area that have any possibility of impacting your location:


We will be using “The National Performance of Dams Program (NPDP)” website to determine two things:

  • The downstream Hazard Classification for the Dams located in our area.
  • The distance the Dam is to the nearest towns.

The NPDP is an excellent website run by Stanford University’s Department of Civil and Environmental Engineering. Inside their website they offer a query system for many dams located in the United States, which can be searched by state. They give you information about the Dam and its Hazard Classification (downstream hazard) plus much more information. But the caveat here is: You need to know the name of the Dam.  [You should of been able to get the name(s) from the previous section using Lat-Long.com.]

  • Click on the Button to go to the site:  NPDP: The National Performance of Dams Program     http://ce-npdp-serv2.stanford.edu/DamDirectory/DamEAPQuery/EAPForm.jsp
  • You can search by Hazard Class: Any, Low, Significant, or High.  Remember, these are classification of the potential damage downstream from the dam –  does not indicate the structural integrity of the dam.
  • Select the State you are searching from the Drop Down Box
  • Go to the Query Result Format section – the box “Ordered by” and choose “Dam Name” from the drop down.
  • And hit the SUBMIT Button
  • You will get a list of dams located in the State you are researching (depending upon the filter parameters you just chose above).  This list is sorted by the Name.  It would be much more usable if it could be sorted by county, city, state, or Zip Code.  But to the best of my knowledge it can’t.  However, if you can get the name(s) of the dams in your area from using one of the above methods, you can look that dam name up on this list and get the Hazard Class for the dam.
  • By clicking on the NPDP ID Number (Left Hand Column) of the dam, you get additional information like: Nearest Town, Distance to Nearest Town, etc.
  • By clicking on the “View More” button for the dam, you can even get more information about the dam.

Due to the limitations of the information that is available for the dams in the United States.   We are going to need to make some basic assumptions: We will assume that any Dams found in the area are capable of failing and it must be assessed.

We will assume the worst case scenario.  When we are evaluating any risks that our families may encounter, we will assume the WORST – and Hope for the BEST.

If you find NO Dams in your area that can impact your location:  Give yourself a Risk Probability of 1.

If you find a Dam in your area that has a Hazard Classification from NPDP classified: Low, Significant or High then assign one of the following Risk Probabilities.

  • Low =  3 – Moderate
  • Significant = 4- High
  • High = 5 – Very High

Now insert your Risk Probabilities for Dam Failure in your Table of “Probability of a Disaster Occurring”.

At this stage of the game – You may want to consider the next step.


If you have discovered that you are located downstream from a Dam that was rated with a Hazard Classification of “Significant” or “Higher”, then you should take it the next step and get more detailed information. As instructed by the US Army Corps of Engineers….

  • Go to this website DamSafety. org   http://www.damsafety.org
  • On the Right Hand Side of the Page – look for an Orange Box called “Information For:”
  • In that section, click on “The States” and you will be taken to a map of the United States.
  • Click on the state you are researching.
  • Get the information for the Contact Person for the State’s Dam Safety Program.
  • Call the contact and explain to them:

°  The address you are researching.

°  You have become aware that you may be downstream from the Dam “Name” that you uncovered.

°  You want to know if your property is located in the Dam Breach Impact Area of the Dam – OR IF THERE ARE ANY OTHER DAMS THAT CAN IMPACT YOUR PROPERTY?


 If you are a little confused about the process of  “Determining Your Risk Level from Dams” – please check out the video below.  It will help make things a little clearer.

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Protection from a Dam Breech.


Let’s face it, the only real protection from a breaching Dam is to get out of the way of the water.  As FAST as Possible.

If you find you are located in a Hazard Area of a Dam – you need to be more prepared to protect yourself than the average person.  You have a unique risk facing you.  Especially after the American Society of Civil Engineers gave the dams in the U.S a grade of “D” in 2013.

Contact the person who is responsible for the Dam Safety Program in your area.   Find out exactly which dams can have an impact on your location, what are the procedures if there is a breech, and how are the alerts distributed.

Sign up for any mailing list, notification programs, or any other information that they may offer.  You can get the contact name and phone number by clicking on this button and click on your state:    Dam Safety Program

Always have a Go-Bag ready – just in case.

Make sure to communicate your Dam Breech Plan with your family members and make sure they understand what they are responsible for and what they need to do if the situation does arise.

Have several escape routes and Fall Back locations planned.  Have plans that include both car and walking escape routes.

Secure your valuables in a water proof safe.  Considering storing semi-valuable items in water proof containers and wrap them in plastic bags and seal them with waterproof tape for extra protection.

Again; if you determine that you are located in an area that can be impacted by a breaching dam – plan on getting you and your family out as fast as you can.

 This is what you should be taking away from this module:


  1. Facts about dams.
  2. Why we need Dams.
  3. The 3 Types of Dams.
  4. The Dangers associated with Dams.
  5. How to located Dams in your area.
  6. How you can determine your “downstream” Hazard Classification – but not a rating of the Dams structural integrity.
  7. How to determine your Risk Assessment for your location if a local Dam does breaches and if necessary, who to call to get detailed information regarding the Dam Breach Impact Area of the Dam.


Side Note: I have to say that this was the most difficult module in Practical Disaster Planning that I had to research. I am still dumbfounded regarding the government not releasing the structural integrity rating for a particular dam. But we must face reality and find other methods to determine exactly what risks our families may be at, and then determine the best way to protect them.

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