3 ms·

All dams have spillways. There are various types and they have several functions: avoiding collapse due to say flooding; allowing controlled release - "spate"

All dams have spillways. There are various types and they have several functions: avoiding collapse due to say flooding; allowing controlled release - "spate" - handy for, say, helping salmon to run upstream - yes it is a bit counter-intuitive. The river Tamar largely delineates Devon and Cornwall in England, UK. It is mostly run off from Dartmoor and hits the sea at Plymouth (which is named after the river Plym). The Tamar is joined by the river Tavy (hence Tavistock, which is a few miles north of Plymouth). The Tamar and Plym run into Plymouth Sound which is the name for the area of sea just south of Plymouth, inside the breakwater. Right, its sodding complicated! The original dam and reservoir for Plymouth and the surrounding areas was Burrator Reservoir. In the 1980s - Roadford Dam and reservoir was built. I studied Civil Engineering from 1989 to 1991 at Plymouth Polytechnic/Poly South West/Uni of Plymouth - it went through a few changes in a short time! Roadford has a bellmouth spillway. Basically there is a plughole with a tube to the Tamar in the base of the reservoir with a concrete tower with slits at a set level. Water is heavy stuff and needs to be treated with care so the spill way attempts to dump as much energy as possible, whilst still shifting as much water as possible to down stream. I left Plymouth in 1996 but I do recall that in 1994 or 5 when there was a dry summer, that a spate was released from Roadford for the salmon. That spate was equivalent to three Burrator reservoirs capacity and it happened over a few days. Oh and Roadford has the river Wolf downstream 8)

pengaru 3y ago
What does spillways have to do with this thread of discussion? They're not generally capable of discharging water down to the original river's level, as they're intended for flood conditions where the reservoir behind the dam is too high. It's the opposite role of what we're talking about. i.e. not a single spillway here[0] is capable of achieving the equivalent of destroying the dam... [0] https://en.wikipedia.org/wiki/Spillway https://en.wikipedia.org/wiki/Spillway
Arrath 3y ago
> All dams have spillways. That's a broad statement that doesn't apply as generally as you suggest. For example, low-head dams generally don't have spillways though in essence function as a spillway. They're entirely passive structures with no mechanism for the owner/operator to change the water impoundment or flow rate.

pengaru 3y ago

What does spillways have to do with this thread of discussion? They're not generally capable of discharging water down to the original river's level, as they're intended for flood conditions where the reservoir behind the dam is too high. It's the opposite role of what we're talking about. i.e. not a single spillway here[0] is capable of achieving the equivalent of destroying the dam... [0] https://en.wikipedia.org/wiki/Spillway https://en.wikipedia.org/wiki/Spillway

Arrath 3y ago

> All dams have spillways. That's a broad statement that doesn't apply as generally as you suggest. For example, low-head dams generally don't have spillways though in essence function as a spillway. They're entirely passive structures with no mechanism for the owner/operator to change the water impoundment or flow rate.