Evacuate Long Before the Dam Breaks!

Here's How to Decide When To Leave
And Then Apply It to Your Situation

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Dam Concerned Citizens has been discussing evacuation and other needs in coping with flood-related issues for several months, and many people have made many suggestions. We gradually came to see the truth that we all knew all along: We must evacuate before the dam breaks. The only problem is determining when. We have a recommendation, and will explain here how you can get the information you need to leave at an appropriate time.

1. Breaking the Dam

The most likely dam break scenario is a gradual increase in reservoir water level until it reaches the theoretical break point, elevation 1,138 feet. Neither the city nor anyone else has indicated that the dam is in such bad shape that it may fail on its own. In fact the engineers believe it will hold for an even bigger runoff than in 1996.

The only things that seem likely to trigger a sudden, unexpected dam failure are a major earthquake or a terrorist attack. If this were to happen there will be nothing but chaos. Therefore we will consider the likely scenario, a gradual increase in water level.

Mild flooding generally starts when the Schoharie Reservoir water reaches an elevation of 1,132 feet. That is two feet over the top of the dam. Moderate flooding generally starts at 1,133 feet and major flooding at 1,135. Short of an earthquake or terrorist attack, we will see deep water long before the dam breaks. The question is obvious: At what water level should you leave?

2. Determining When to Leave

We think that Schoharie County residents of Schoharie Valley should seriously consider leaving at the commencement of flooding. This is a water flow rate of approximately 10,000 cubic feet per second. Current flow rates are available in two places, as we will explain below.

Note: We are making this recommendation for valley residents of Schoharie County and the recommendation is 10,000 cfs and rising. There are circumstances when people may need to start evacuation earlier, for example if you have bedridden people who must be evacuated. Some people who reside in Middleburgh, Schoharie and Esperance may feel comfortable remaining in the valley until 15,000 cfs, and there is no reason they should not select some reasonable number other than 10,000 cfs. Most of us are usually here through even greater floods.

This is an amendment to our original recommendation which was based on 1,132 water level elevation, because with the notch in place the 10,000 cfs flood level will be reached before water reaches 1,132 feet.

Montgomery and Schenectady county residents will have many more hours in which to act because we know from past experience that it takes hours for water to move from Gilboa to Esperance, and even more to reach the Mohawk. Yes, we expect that in a dam break, water will move faster. But that is exactly the point of our recommendation: We must get out before the dam breaks because when it does break, chaos will occur.

These are the things that we considered in deciding to recommend evacuation when water reaches 10,000 cfs in Glboa. If your circumstances are different, choose a different number.

• Short-term weather forecasts are very accurate but meteorologists cannot accurately predict every storm or every location.
• Water from many tributaries is not measured and therefore no guide is available. While elevation 1,132 and flow rate of 10,000 cfs generally indicate the start of flooding in low-lying areas, exceptionally heavy rainfall north of the dam (downstream) may  start flooding at lower numbers.
• One will need several minutes – perhaps a half hour or more – to get everything needed into the car, especially if you have children or pets.
• At a time which is different for every flood, roads start to become impassable. At a later time, bridges start to fail. It is necessary to evacuate before any of that happens.
• Traffic will increase as residents decide to evacuate. This will be compounded by closing roads and increasing highway emergency traffic and situations.
• At some point which has probably been determined but which our government won’t tell, officials will start closing roads and telling us to leave. Don’t wait for road closure. Leave before chaos erupts.

Clearly, the earlier we leave, the better. Rising floods only get worse and we cannot know when the flood will start to drop.

As stated above, people who have special circumstances may wish to leave earlier and they should not hesitate to do so. And since 10,000 is a low level of flood, you may feel comfortable staying longer.

It is important to decide many things long before the flood, and first on the list should be when you are going to leave. Err on the side of caution.

3. Notification and Obtaining Information

3A. Broadcast Resources

Commercial broadcast stations use “EAS,” the Emergency Alert System, to broadcast flood watches and flood warnings put out by the National Weather Service. This can be your first notice that trouble is brewing. Immediately start monitoring the situation. There are multiple alternate sources of the EAS warning. Some are: WGY ( 810) and WROW (590) on AM radio, and WMYY (97.3) and WYJB (95.5) on the FM band. Many other stations also carry the information.

The Weather Service operates a special notification service called NOAA Weather Radio. Albany and Binghamton weather centers broadcast in this area. 162.55 megahertz is the frequency used by Albany and 162.40 is used by Binghamton. In addition to the constant broadcast of weather forecasts, coded alarms are broadcast for emergency situations.

Emergency weather radios receive these coded signals and sound a loud wake-up alarm and display a message. NOAA weather radios can be purchased at many places and have been distributed in the valley by local emergency officials. Those were provided by New York City. If you live in the flood plain in Schoharie County and do not have one, call the county emergency management office in Schoharie to obtain one for free.

A major problem with these is that reception is not good in much of the valley. Some false signals have also been picked up. Another problem is that they must be programmed properly. If you do not fiddle with adjustments well, find someone who does.

The major advantage of these radios is that when the emergency alert is received, a loud wake-up alarm sounds. They will not give you water flow or elevation numbers but they will wake you up.

The Schoharie county dispatch center broadcasts water flow every half hour during high water situations, on frequency 46.180. Most scanner radios can receive it when programmed. You’ll get cfs numbers here, and a lot of other messages on it too. The water flow reports will be in the form, “11,000 cfs at Prattsville and rising” and will be given for Prattsville and a station at the Blenheim-Gilboa power project.

3B. Internet Resources

Do not despair if you do not use the Internet. Some of the best resources are there and you probably know someone who does use Internet. Adopt that person.

National Weather Service gives forecasts for many localities. They are available at www.weather.gov where you may put in a city and state, or zip code.

NWS Advanced Hydrologic Prediction Service provides a hydrograph chart with a number from a measuring device. At some places, the measurement is stream level, such as 6 feet. At Gilboa Dam it is related to the 1,130 dam elevation. The charts are “live” (frequently updated during the day).

The USGS graph showing cubic feet per second below the dam is you best predictor. It is at http://waterdata.usgs.gov/ny/nwis/uv?dd_cd=01&format=gif&period=7&site_no=01350101

These Gilboa charts are shown or linked on our home page.

The Gilboa Dam water elevation chart is at http://newweb.erh.noaa.gov/ahps2/hydrograph.php?wfo=aly&gage=giln6

The master chart showing other stations in this area us at http://newweb.erh.noaa.gov/ahps2/index.php?wfo=aly

4. Understanding the Numbers

These levels have been worked out over the years

1130 is Gilboa Dam elevation in feet
1132 is flood stage
1133 is moderate flood stage
1135 is major flood stage
1136.6 is the record storm of 1996
1138 is the point at which the dam will, theoretically, break

Cubic feet per second (cfs) measurements are taken at various locations. Prattsville and Power Authority numbers are broadcast on the fire frequency every half hour when high water is in progress. Ignore the Prattsville number excepting as a directional guide (riding or falling).

10,000 cfs is flood stage
20,000 cfs is moderate flood stage
40,000 cfs is major flood stage
70,800 cfs was reached Jan. 19 1996
89,200 cfs was the theoretical break point prior to notching
100,000 cfs is the risk point after notching
These are Gilboa Dam numbers. They’re a fair guide for responding to what you will hear on the fire radio, 46.180

5. Making A Plan

Know here you are going to go for current information. If you do not have a scanner or computer, do you have a friend or neighbor who does?

Decide when you are going to leave: 10,000 cfs or more? Are you going to leave on a prediction or an actual flood level?

Consider alternate scenarios. You may have to leave at night and you may have to leave from home or work. Be ready for each.

Know where you are going to go. Friend? Relative? Know the routes. Decide what to take for people and for pets. Take medicine and vital information as well as food and water. Assembly three days of supplies to tale with you – food, water, clothes etc.

Lock your doors when you leave.

6. Getting There

Consider vehicle failure and think about a alternative evacuation ahead of time. Review your entire route. Areas will be cut off and at some time, bridges and roads will wash out at some time. Look for circumstances or for places along your route that may strand you

7. Execute Your Plan

Rehearse your plan – drive your evacuation routes at night.

Stay on top of the weather situation at all times.

Since we presented this at a meeting on February 9 in Schoharie, people have made many more valuable suggestions. We will be making a list of these to post in the next few days.

Posted 10 Feb 2006
Modified 17 February 2006
Reviewed & updated 21 November 2008