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Wednesday, August 24, 2011

LYNN BERGMAN: UNDERSTANDING NORTH DAKOTA FLOODING - PART I

The Ugly

The first hints of the answer came in late winter. I was enjoying the last days of cross country skiing at Riverwood Golf Course. I noticed that four steel trail markers had just fallen over. It had been difficult to pound them into the frozen ground when they were installed in the early winter of 2010. I re-pounded them into the soft ground easily. With well over a foot of snow on the ground all winter long, the frost was out of the ground before the daytime highs exceeded 32 degrees.


I was not surprised when the Corps of Engineers announced that outfalls from Garrison dam would approach 65,000 cfs (cubic feet per second). The snow cover in the mountains of Montana begins to melt in late June and seriously in July and August when the highest temperatures occur.


When the Corps announced only days later that 150,000 cfs would be released, I bought into the explanation that around seven inches of rain on the plains of Montana was the reason. But the underlying conditions were to come to me later.


About mid-May it suddenly came to me what the difference was between 2010-11 and prior years. Heavy snow melt in the Mountains was a usual phenomenon. But an average of almost two feet of uniform snow cover on the upper great plains is just not normal. The prairie winds usually re-distribute the snow, leaving vast areas of flat land with little snow cover and the low areas downwind of ridges and other obstacles filled to the brim with wind-blown snow to depths as high as 5 feet to 15 feet. As snow on the upper great plains melted in early spring of 2010-11, however, runoff was minimal. As high daily air temperatures approached 32 degrees, the soils underneath the snow melted the snow from the heat of the earth below and the soils of the upper great plains became uniformly and deeply super-saturated without any significant runoff overland. Normally soils accept around 65% to 95% of rainfall, with the average being about 80%. When the heavy rains fell in Montana and North Dakota, the reverse was probably true; infiltration was likely as little as 20% with 80% of the rainfall running overland. This is why the dams filled quickly, causing the problems we are still dealing with.

The Bad

But it is not quite so simple as the “natural hydrologic causes” outlined above. There were underlying mistakes made by man long before the “natural” snowmelt and rainfall that occurred this spring and summer. The underlying reasons are threefold.


First, recreational interests have taken far greater priority in the Corps Master Manual than they should have. And siltation of the reservoirs behind the dams is significant, as was found during construction of the new Four Bears bridge. This lack of volume must be compensated for in setting the maximum pool levels. For these reasons, maximum pool levels for the dams are too high.


Second, environmental interests have likewise been given too much priority. The nesting of piping plovers and least terns should be a consideration but should not necessarily dictate low flow rates during the spring when they are nesting. When necessary during years of high mountain snowmelt, they will find other sources of gravel to nest on, such as the areas on mines where topsoil has been removed and gravelly soil is exposed.


Third, while shipping downstream of the Missouri dam system has decreased significantly in economic impact to the country, the concern for minimum flows for shipping has  lead to the retention of higher maximum pools so enough water is available for shipping.

The Good

The good news is that it is extremely likely that the master manual will be revised to correct all of man’s mistakes. And the normally relaxed government employees will be “on their toes” for some time to come.


Further, there is no logical reason why homes values in the areas where homes have been flooded should go down. This was a one time disaster that served as a wake up call to the managers of the dams that filled so quickly this year. The dam managers will not repeat the mistakes that exacerbated the natural conditions that were also unusual.


So please do not be too hard on the Corps of Engineers. They employ some of the best hydrologic, hydraulic, and structural engineers on the planet; and the worst political environment possible, with less then competent politicians having been looking over their shoulders for decades. That micromanagement by politicians must end and be replaced with logic and vigilance that is maintained over time.


The real problem will come decades from now when the high dams are all filled up with silt, something the original designers knew would happen eventually, but ignored because it would not happen in their lifetime and because of the pomposity of politicians in believing that nature can be tamed. So a moratorium of all new building of habitable structures within the natural overbank of the Missouri is an additional necessity.


Mr. Bergman was born and raised in Grand Forks, receiving his Civil Engineering degree from UND. He worked as a municipal engineer in four cities (Grand Forks, Bismarck, Yuma, Arizona, and Colorado Springs, Colorado) over a period of almost 20 years. He then worked for a mining company in North Dakota for another 15 years, retiring in 1998. Development and demonstration of Portland-pozzolan cement and optimally durable concrete has been one of his life’s passions. Political activism is another interest and he is a Director of “Citizens for Responsible Government”, an organization devoted to fiscal responsibility in government. He is President of DuraCement, LLC.


© 2011 Lynn A. Bergman

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Comments

“Missouri River Overbank Area Moratorium” Clarification:

A permanent moratorium would be on “all new habitable structures” except those to be constructed within previously platted subdivisions (to avoid needless lawsuits).

Improvements like warehouses, repair shops and other commercial operations and all other uses compatible with zoning laws would be fine. It is the construction of schools, houses of worship, homes, and other structures where one or more person sleeps overnight or where over a couple dozen people congregate during the day that must be curtailed.

The reason: with continued siltation behind the dams, either a catastrophic failure or a controlled conversion to pre-dam construction conditions is inevitable decades from today. It is time to PLAN to “give the the Missouri River back to nature” within 50 years.

Lynn Bergman on August 25, 2011 at 11:06 am
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