Get this from a library! Freeboard allowances for waves in inland reservoirs. [ Thorndike Saville; Elmo W McClendon; Albert L Cochran]. Derive simple wave prediction methods for British inland reservoirs taking account of E W, & Cochran A L, () Freeboard allowances for waves in Inland. overtopping due to wind-generated waves and reservoir setup. • Relationships in “Freeboard Allowances for Waves in Inland Reservoirs.
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The effective fetch method supposes that a directional diffusion of the wind in cosine from the 10th power, starting from the maximum frequency of the wave spectrum and taking into account the distance Fi which separates the border of the damevery When the waves hit the upstream face of the dam, we assist in an upsurge of the water level due to the fact that the kinetic energy in the waves is transformed into potential energy.
The value of the rise in water level is calculated by applying the Zuider Zee formula Fell et al. Historically, we usually work with the significant height. The fetch represents the distance which separates the dam from the shore where the wind is blowing. Characteristics of wave spectrum. Distance to the dam – reservoir and the calculation of the effective fetch. Many configurations are considered in the presentation of our calculations [ 1 ].
The objective of evaluating the freeboard is to provide needed assurance against overtopping resulting from the following: Determining the wave run-up height. The development objective of the Lom Pangar Hydropower Project for Cameroon is dreeboard increase hydropower generation capacity and reduce seasonal variability of water flow in the Sanaga River and to increase access to electricity [ 7 allowabces, 8 ]. Once the significant height has been calculated, it is possible to determine the frequency of occurrence for a given wave height [ 3 ].
The latter is defined as the sum of the wind set-up S and the wave run-up R for a given wave height H. This paper has as purpose to show the calculations done to determine the upstream freeboard the difference in height between the highest level of water upstream and the crest of freeboarr embankment for the Lom pangar dam in Cameroon. The freeboard f is defined as the difference between the height of the dam crest and the maximum elevation attained by the waves on the upstream ij of the dam.
An average depth of 30m has been retained in the ensuing calculations. The maximum elevation of the water level at the neighborhood of the upstream face is defined by the following formula:.
A model of the phenomenon caused by wind. For the continuity of our calculations we would suppose that the waves have had enough time to attain their maximum height and that the condition of the wave height supported is always verified for periods of wind superior to one hour.
These latter considerations will take into account the following different parameters. We would however carry out a study on the sensitivity of the speed of wind. Journal of Engineering and Technology.
This increase in the height of the waves is called wave run-up. Table 4 and 5 synthesize the results obtained for the laterite backfill embankment as well as the transition cor fill embankment. This length is called the effective fetch and denoted Fe.
Freeboard Allowances for Wave in Inland Reservoirs
For each of the configurations considered, the criteria for expected minimum freeboard in table 1 are respected for all the dams considered. Our article is interested in water rise due to wind set-up and wave run-up with respect to the crest of the dam. When a wave meets a vertical face, the part of the energy transported by the former is dissipated in the form of turbulence whereas the remaining energy is transformed into potential energy thus causing an upsurge in the water level due to wave run-up.
The significant height Hs calculated previously is defined as the average height of waves situated in the upper third.
Freeboard Allowances for Wave in Inland Reservoirs
H is defined as the average height of waves over the percentage of the highest waves. The calculation of minimum freeboard alowances the embankment dam. As we can see in table 3thirteen percent of the waves go above this height. Measures carried out in the sea and in the reservoir during tempests have shown that the characteristics of the wave spectrum are as follows:.
The RCC dam — Calculation of freeboard. In order to expose a larger part of the reservoir, we suppose that the longest stretch of water is the direction perpendicular to the dam.
When Z reservoiris The impact height of a wave is a combination of an upsurge in water level and run-up height R associated to a wave height H in deep water.
Laterite Embankment fill at 3. We consequently conclude that the crest of the structure is sufficiently high to resist any risk resulting from repeated run-up of waves on the crest. The waves generated by reservoird wind under the hypothesis of great depth do not have the same height. The average of rise in water level is a result of the blowing of the inlanv. The submersion of an embankment due to waves could affect its lifespan and it is thus necessary to verify the height freeeboard the crest of the dam in a ffeeboard that would protect it against a maximum increase of inlznd water level.
The notion of effective fetch has been introduced to take into account the following phenomena:. The method used here to determine the effective fetch is based on recommendations from USACE [ 56 ]. Transition embankment at 1.