Thank you very much David, Neil, Wurzel and Pauline,
Regarding BBC Breakfast report 06:50 on May 4th 2014 The River Mole Survey of Flood Damage to the main flood channel.
This stretch of the River Mole was local to me. I grew up around here.
Basically, the part of the River Mole (lower reaches) filmed on the BBC Breakfast report, appeared to do its job quite well in regard to carrying the water away quickly after the winter floods further upstream. The main flood channel was generally, not good for fish. It was too uniform in low water conditions to stop cormorants rampaging through fish stocks. The cormorants might otherwise have kept to the local reservoirs, as was the case many years ago, or so I was told.
When the river was in spate, many of fish left for example, Roach, Bream, Perch, Pike, Chub & Dace along this stretch of the Flood Relief Channel, were literally thought to have got washed into the River Thames and could be found on an average year, when the Thames hadn't flooded as well, near the Molesey Weir, on the Thames in the Summer.
When designing these "flood channels", it was thought there needed to be more of a fish friendly approach including more areas where the fish can shelter, when the river was in spate and more attempts to slow the water a little to reduce bank erosion but still keeping the potential to carry water away quickly. A good test for a newly designed flood channel was to wait 5 or 10 years and then see if there were many or any Roach and Bream present in mature sizes, as these species suffered most from a "forced migration downstream" during floods.
It looked to me, like most of the bank erosion took place a short distance downstream of the weir at Esher.
The lower stretch of the River Mole flooded more frequently 35 years ago, despite the ever changing river course. Back then it was a wildlife haven and the weirs were fully automatic. I think the Environment Agency might do better in the future, when similar flood channels were designed.
Turning my attention to Butterflies. Regarding the picture below taken on May 5th 2014. I knew it looked pretty but Oil Seed Rape on the river banks? Was that a good plant to have here? I would suggested that it might not be the best apart from its aesthetic appeal. Any more information on this would be much appreciated.
Updated April 30th 2020: Oil Seed Rape was a brassica, so might have been good for Small White butterflies and Large White butterflies, to help complete their life cycles.

- Grid Ref. TQ130660 River Mole Flood Channel

- Plenty of Butterflies on the "Man made" river bank

- Downstream of the main weir at Esher

- "Flow Measuring Station"
In all I saw, Small Whites, Large White, Brimstones, Peacocks, Green-veined Whites, Holly Blue and Orange Tip butterflies,
Best Wishes, Philip