In a previous post, the shape of the induced surcharge envelope curve was discussed.
That post is located here:
Development of Induced Surcharge Envelope Curve
In that post, the portion of the curve shown in green in the figure below was examined. The purpose of this shape at the beginning of the curve is to increase benefits for more frequent events by having less of an increase in discharge per change in elevation. As the event becomes more severe, the slope becomes flatter, which leads to greater increases in discharge per change in elevation.
It may be desirable to attempt to extend the greater downstream benefits for less frequent events by further altering the shape of the curve. In the figure below, the steeper slope is extended further. If the elevation at which the spillway gates are fully opened remains unchanged, the slope of the remaining portion of the curve needs to become very flat which increases the rate of change in discharge per change in elevation. This can make it more difficult for real-time reservoir operations and lead to a less desirable result if the event becomes more severe.
In the figure below, the steeper slope is also extended further. This time, however, the remainder of the slope is consistent with the original curve. This leads to a higher elevation for fully opening the gates. In order to implement the updated curve, the same considerations used for the development of the original curve need to be taken into account. These considerations include, but may not be limited to the following:
That post is located here:
Development of Induced Surcharge Envelope Curve
In that post, the portion of the curve shown in green in the figure below was examined. The purpose of this shape at the beginning of the curve is to increase benefits for more frequent events by having less of an increase in discharge per change in elevation. As the event becomes more severe, the slope becomes flatter, which leads to greater increases in discharge per change in elevation.
It may be desirable to attempt to extend the greater downstream benefits for less frequent events by further altering the shape of the curve. In the figure below, the steeper slope is extended further. If the elevation at which the spillway gates are fully opened remains unchanged, the slope of the remaining portion of the curve needs to become very flat which increases the rate of change in discharge per change in elevation. This can make it more difficult for real-time reservoir operations and lead to a less desirable result if the event becomes more severe.
In the figure below, the steeper slope is also extended further. This time, however, the remainder of the slope is consistent with the original curve. This leads to a higher elevation for fully opening the gates. In order to implement the updated curve, the same considerations used for the development of the original curve need to be taken into account. These considerations include, but may not be limited to the following:
- Upstream flooding considerations
- Dam safety considerations
- Access to the spillway gate controls
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