GoldDredger
Civil/Environmental
- Jan 16, 2008
- 172
I've come across an interesting situation, let me give some background.
Three 48" road culverts convey upstream flow between two private lots before reaching the river. The soil characteristics are sandy silt with little cohesive strength.
The drainage shed is approximately 130 acres, with a current 100 year flow of about 180 cfs (recently experienced). The future build out upstream will increase that flow to about 400 cfs.
The channel between the two lots is experiencing extreme erosion, much to the chagrin of the two owners. We will propose a concrete or armored channel for the majority of length between the culverts and river.
However, there is one area which coincides with the historic 100 year WSE of the river, where a large drop off is evident.(see picture attached) The picture is a bit misleading, the drop from top to bottom is about 25 feet.
We will have some fill brougt in to raise the bottom and begin the channel, however I plan on designing a spillway from the top to toe at this drop area.
Can anyone refer me to some standard details for spillways. I was thinking maybe an ogee spillway design with a trapeziodal channel at each end. Or, perhaps just a linear channel down the slope, but I am worried about the hydraulic jumps where the flow will likely go from sub-super-sub critical.
Anyway, I am looking for a detail of a spillway.
Three 48" road culverts convey upstream flow between two private lots before reaching the river. The soil characteristics are sandy silt with little cohesive strength.
The drainage shed is approximately 130 acres, with a current 100 year flow of about 180 cfs (recently experienced). The future build out upstream will increase that flow to about 400 cfs.
The channel between the two lots is experiencing extreme erosion, much to the chagrin of the two owners. We will propose a concrete or armored channel for the majority of length between the culverts and river.
However, there is one area which coincides with the historic 100 year WSE of the river, where a large drop off is evident.(see picture attached) The picture is a bit misleading, the drop from top to bottom is about 25 feet.
We will have some fill brougt in to raise the bottom and begin the channel, however I plan on designing a spillway from the top to toe at this drop area.
Can anyone refer me to some standard details for spillways. I was thinking maybe an ogee spillway design with a trapeziodal channel at each end. Or, perhaps just a linear channel down the slope, but I am worried about the hydraulic jumps where the flow will likely go from sub-super-sub critical.
Anyway, I am looking for a detail of a spillway.
