Flood Resilient scheme £0.25m most happen significantly reducing River Calder flooding for Mirfield
Install a spillway, or extension of weir downstream of Shepley Bridge
A spillway, or extension of the weir set at the same datum level 39.630m AOD as the existing weir would not affect the water level of the weir nor the Hebble Navigation.
As you can see from my video https://www.youtube.com/watch?v=a66uatM3SrA which was taken at 3.30 pm 26th December 2015 the outcrop of land between the Ship-inn and the weir is submerged by flood water, my calculation indicates between 60 and 70 cubic meters p/s past over this point and continued to do so over a 2 hour period within this timescale Ravensthorpe nor Dewsbury downstream of this area flooded.
The outcrop of land removes the energy from the flow restricting slowing the movement of water. However, if a spillway or extension of the weir was constructed between the wier and Shepley Bridge I would expect the spillway or extended weir to remove 19 cubic meters of flood water per second, for one minute this would remove 1.140 cubic meters the equivalent to a football field one meter deep. This would have significantly reduced flooding on Boxing day 2015 across the footprint of Mirfield River Calder and creating a faster flood water retreat with less debris left behind over than the main river channel.
This also would significantly reduce the number of times Steanard lane floods. Computer Model River Calder foot-print Mirfield Flow Rates 2015
The model is showing some interesting results, and pointing to answers to reducing flooding across the river Calder footprint of Mirfield. On Boxing day 2015 time 3.30 PM at Ledgard bridge Mirfield 453.6 cubic meters per second of water past this point. To understand in more detail the benefits which a spillway or extension of weir at a rate of 19m3 P/S or more would mean for Mirfield,
Ledgard bridge Mirfield chart indicates flood is possible at 2.52, and stared 25th December 2015 9.0pm and peaked at 5.30pm 26th December 2015 which was 20 hours later. spillway or extension of the weir would have activated at 2.52,25th December 2015 9.0pm and continued to work throughout the event.
However with the evidence 60 and 70 cubic meters p/s past over the outcrop of land at Shepley Bridge and continued to do so over a 2 hour period within this timescale Ravensthorpe nor Dewsbury downstream of this area flooded. I believe we could safely increase from 19m3 l/s to 45m3 l/s?
For an example would be the storm which closed the Ship Inn on the 13th December 2015 The chart quite clearly shows the peek of the flooding at 9.00pm 13th December 2015, however, the outcrop of land at Shepley Bridge was not submerged by flood water throughout the event.
Releasing an extra 19m3 P/S over the 3-hour period would have allowed 205,200 cubic meters to past the weir and the Ship Inn would not have flooded. based on the events of 13th December 2915.
River Weir 6, Battyeford = 45.279m AOD River Weir 8, Greenwood Shepley Bridge = 39.630m AOD. Calder footprint across Mirfield reach is approximately 4.5km over that distance gives a fall of 0.5649 it would take 11.63 minutes for the water to travel this distance
From the video footage, and photos from the 26-12-2016 All the calculation are from timescale 3.PM – 5.PM and re-visiting the areas, calculating depth, and square meters with a little guesswork? I now can estimate the volume of flood water which Mirfield floodplains off-line storage held.
- The playing field at John Cottons floodplains this area held, and released 38,220.0 cubic meters of flood water.
- Calder view floodplains this area held, and released 49,322.0 cubic meters of flood water.
- Calder views exit road this area held, and released 4,804.0 cubic meters of flood water..
- Huddleston Court at this area held, and released 3,118.0 cubic meters of flood water,
- Newgate at this area held, and released 612.0 cubic meters of flood water.
- Station road at this area held, and released 1,489.0 cubic meters of flood water.
- Allotments floodplain at this area held, and released 19,152.0 cubic meters of flood water.
- . Walkers factory floodplain at this area held, and released 48,021.0 cubic meters of flood water.
- Lowlands at this area held, and released 32,670.0 cubic meters of flood water.
- Between Walkers factory, DR Reddy’s floodplain at this area held, and released 43,010.0 cubic meters of flood water.
- DR Reddy’s floodplain at this area held, and released 15,758.0 cubic meters of flood water.
- .Steanard Lane at this area held, and released 2,928.0 cubic meters of flood water.
The grand total of flood water offline storage on Boxing day 2015 calculates to 259,104.00 cubic meters of flood water. This can also be multiplied by 120 minutes which is the two hours from 3.30.PM – 5.30.PM and this is the time scale which most of my date was collected?
If an extra 19 cubic meters of flood water per second past the weir at Shepley Bridge over the 2 hour period 136.800 cubic meters would have past downstream, take that from 259,104.00 0ffline storage = 122.304 cubic meters over the 2 hour period significantly reducing the amount of offline storage for Mirfield.
Please don’t hesitate to contact me on this matter