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 latter is defined as the sum of the wind set-up S and the wave run-up R for a given wave height H. 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.
Once the significant height has been calculated, it is possible to determine daves frequency of occurrence for a given wave height [ 3 ]. An average depth of 30m has been retained in the ensuing calculations.
As we can see in table 3thirteen percent of the waves go above this height. 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 the embankment for the Lom pangar dam in Cameroon. The objective of evaluating the freeboard is to provide needed assurance against overtopping resulting from the following: For each of the configurations considered, the criteria for expected minimum freeboard in table 1 are respected for all the dams considered.
Journal of Engineering and Technology. Laterite Embankment fill at 3. For the continuity of our calculations we would suppose that the waves have had enough time reservors attain their maximum height and that the condition of the wave height supported is always verified for periods of wind superior to one hour.
Freeboard Allowances for Waves in Inland Reservoirs
The waves generated by the 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 wind. Historically, we usually work with the significant height. Determining the wave run-up reservoits. The significant height Hs calculated previously is defined as the average reservolrs of waves situated in the upper third.
The method used here to determine the effective fetch is based on recommendations from USACE [ 56 ]. The RCC dam — Calculation of freeboard. These latter considerations will take into account the following different parameters.
Freeboard Allowances for Wave in Inland Reservoirs
The development objective of the Lom Pangar Hydropower Project for Cameroon is to increase hydropower generation capacity and reduce seasonal variability of water flow in the Sanaga River and to increase access to electricity [ 78 ].
H is defined freeoard the average height of waves over the percentage of the highest waves. 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 reeervoirs distance Fi which separates the border of the damevery When the waves hit the upstream face of the resetvoirs, 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.
This increase in the height of the waves is called wave run-up. Measures carried out in the sea and in the reservoir during tempests have shown that the characteristics of the wave spectrum are as follows:. Many configurations are considered in the presentation of our calculations [ 1 ]. A model of the phenomenon caused by wind.
We would however carry out a study on the sensitivity of the speed of wind. The calculation of minimum freeboard for the embankment dam. 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.
This length is called the effective fetch and denoted Fe.
Freeboard Allowances for Waves in Inland Reservoirs
When a wave meets a vertical face, the part of wavew 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. Characteristics of wave spectrum.
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.
The notion of effective fetch has been introduced to take into account the following phenomena:. Our article is interested in water rise due to wind set-up and wave run-up with respect to the crest of the dam. The submersion of an embankment due to waves could affect its lifespan and it is thus necessary to verify the height of the crest of the dam in a way that would protect it against a maximum increase of the water level. The maximum elevation of knland water level at the neighborhood of the upstream face is defined by the following formula:.
Table 4 and resrvoirs synthesize the results obtained for the laterite backfill embankment as well as the transition rock fill embankment. 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 face of the dam.
When Z reservoiris Transition embankment at 1. Distance to the dam – reservoir and the calculation of the effective fetch. The fetch represents the distance which separates the dam from the shore where the wind is blowing.
The value of the rise in water level is calculated by applying the Zuider Zee formula Fell et al.