Posted: Feb 19, 2020 4:05 pm
Alan B wrote:Cito di Pense wrote:Alan B wrote:The recent severe flooding in the UK attributed to unusual heavy rainfall (which in turn may be due to Climate Change) has made me ask the question: Has an increase of just a few cms or so in the sea level caused a tendency for the rivers to flow more slowly into the sea and 'back-up' thereby contributing to the excessive flooding with rivers bursting their banks and other anti-flood defences?
Has anyone carried out research into sea level and river flow and how much change in sea level can cause a particular change in river flow?
Water is a fluid, Alan. You can't make dams out of water.
If the sea level rises a river's rate of flow into the sea could decrease. This could cause 'overflowing' upstream.
Flooding happens because there's too much water in the channel -- because there's too much runoff in the drainage basin that feeds into that channel.
If you're thinking about the UK flooding, it's because there was a lot of rain. Some channels could not contain the flow.
The volume rate of the flow is related to the gradient (gravity) and then to the cross section area of the channel. The average gradient of a stream that runs for tens of kilometers and descends only tens or hundreds of meters is not changed appreciably by the fact that the terminus of the stream hits water that is centimeter higher than without sea-level rise. Flooding is happening far from this terminus in many cases.