13 May 2012

During the recent heavy rain water levels rose a good deal on the Bulstake Stream. A Flood Alert (the lowest degree of concern) was issued by the Environment Agency.

The new flood culverts under Willow Walk were filled to capacity, not with water coming off the meadow to the north, but from the channel running along the ditch on the north side of Willow Walk from the Bulstake Stream. Water also flowed into King George’s Meadow and Oatlands Road Recreation Ground at quite an alarming rate. In fact there was no control of water flows from the Thames into the Bulstake Stream at Tumbling Bay as the fixed height weir at Tumbling Bay had been over-topped. The Thames had breached the west bank upstream of Tumbling Bay (it does this very early), so this water was filling the fields and then working its way back into the Bulstake Stream by Helen Road. The Seacourt Stream was also pushing water down the Botley Stream into the Bulstake.

The Thames at Donnington was well down; the flood plain upstream from the A34 was empty and so was the flood plain above Swinford Bridge. The new sluice gate (allowing water from the Thames into Osney Stream) on the corner of North Street and East Street remained shut and certainly the Osney Stream could have taken more water.

Some questions:

What is the philosophy on how the Thames is controlled at high levels? Why was the Thames at Donnington low yet the Thames above Osney was bank high? Why was the flood plain above the A34 empty?

Should the west bank above Tumbling Bay be repaired, so stopping water getting into the flood plain at this near-property point until later, not at the beginning of an incident?

How does this last relate to the lack of control at Tumbling Bay, where there is (now) a fixed weir? If more water had been allowed to flow through Osney Lock down towards Donnington the bank at Tumbling Bay may not have been breached.

Should the new gate at North Street have been opened?

We note there is no control of water entering the Seacourt at its origin from the Thames: the weir there is now fixed (it used to have movable boards for control).

In the event, all ended well this time, the water subsiding before any properties were flooded. Our observations and questions are, nevertheless, reasonable and merit consideration by the flood risk management authorities.