Flooding in the High Street

Residents on the north side of the High Street, roughly between the Methodist Church and the Elephant and Castle pub, have been subjected to flooding over the last few months, with water making much of the the pavement impassable without wellington boots and lapping up to their front doors. To the rear of the properties, where the gardens run down to the Misbourne, most of the gardens have been inaccessible for much of the time. The flooding extends to the opposite bank where sports pitches have been unusable.

Martin Brooks, former Chair of the Amersham Society and a High Street resident, believes that the flooding is not the direct result of heavy rain over the Christmas period because the problem extends back over the previous months. Whilst admitting that he is not an expert on flood prevention, Martin thinks that the problem is due to a partial blockage in the tunnel conduits under the Maltings, between Barn Meadow and Pondwicks Meadow. The cause may be twigs and branches from the willow trees along the river, as a result of inadequate maintenance. One of the difficulties is the shared responsibility between the Environment Agency, Bucks County Council, Children District Council, Amersham Town Council and the relevant landowners, with no obvious lead.

Update: since posting the above, the have been a number of developments.

1 The Environment Agency carried out a survey of the tunnel at The Maltings and found an obstruction which, as suspected, is the cause of the flooding.  The original intention was to appoint contractors  to clear the obstruction within the two weeks. A grill would then be installed to prevent a recurrence of the blockage.  However, to clear the obstruction they had planned to dam the river with sandbags and pump water around the culvert so their staff could work safely in the river & culvert. Because the river levels in the Misbourne were so high, the river does not currently have the capacity to take any extra water without risk of causing flooding to the people that live downstream.

2 Continuing heavy rain then resulted in a number of houses and businesses on the north side of the High Street being flooded, as had been feared.

3 With the agreement of the landowner where the blockage is, the Environment Agency then brought in contractors who jetted the obstruction using high pressure hoses. This partially cleared the blockage, mainly of silt and twigs, improving the water flow. However a tree trunk apparently remains and to remove this damming will be necessary. More jetting may be attempted but it does appear that it has been partially successful in that the flood waters in the High Street are receding.

4 Some weeks later, ten tons of silt and rubbish were cleared from the river and it is now in full flow. We have established that Chiltern District Council are taking the lead on setting up a plan for the  future maintenance of the River and the Emergency Planning Officer is organising a meeting of representatives from the various interested local parties . The Amersham Society has expressed an interest in being invited to join that meeting and to be involved with helping in any way we can.

Martin's letter to local Councillors is reprodiced in full here:

 Attention: Old Amersham Councillors

I wanted to escalate the issue of localised flooding of the River Misbourne on High Street pavements, residential gardens and Barn Meadow, as I believe this is probably an issue of poor preventative maintenance rather than that of the recent heavy rainfall. Chiltern District Council (CDC) staff did arrive this week and provide us with sandbags and an information leaflet for which we are very grateful.
1. Summary
This is not a temporary winter problem, for but has occurred last August as well for the first time in summer over the last  35 years in Old Amersham. There is localised flooding extends from the drain by the Methodist Church along the High Street, to residents' gardens to the rear flooded directly from the river, as well to Barn Meadow. The probable cause is partial blockage by vegetation the tunnels that convey the river under the Maltings between Barn Meadow and Pondwicks Meadow. River flow above and below Barn Meadow appears to be relatively normal for this time of the year. A coordinated preventative maintenance programme needs to be put in place for the future involving the three tiers of local authorities , the riparian owners including Amersham Town Council, together with the Environment Agency. Who should lead this needs to be determined.
2. The Problem
This affects my property at 139 High Street and those of my immediate neighbours as well as the "Eagle." The rear garden of my house has been flooded on many occasions both in the winter and summer in the last year, as well as the pavement on the High Street to the front of our houses.  The street is flooded, probably  due to "backwardation" of water flow in a drain that normally flows into the river next to the Methodist Church making the pavement near impassable to anyone not wearing waterproof boots. All this is illustrated in the attached photos.
Last summer in early August was the first time I can recall in over 30 years living here that this flooding occurred in the summer and subsequently, it has been particularly alarming over this period of intense rainfall over the Christmas and early New Year period. So it is turning out to be an extended problem, unlike previous temporary flooding and now detracts from the amenity of Old Amersham, use of our gardens and public spaces and causes affected residents a high degree of anxiety. The current flooding has been happening since well before Christmas. In addition it is leading to a loss of amenity of Barn Meadow and revenue to ATC as the bottom football pitch is flooded and unusable.
3. The Probable Cause
I have discussed the matter with two representatives from the Environment Agency  (EA) who reviewed the situation on Christmas Eve in Old Amersham. Their conclusion is the same as mine; namely that the tunnel conduits that take the river under the rear of 127 High Street and the Maltings  (Mr McLatchie) have become partially blocked, mostly it is a reasonable surmise, with willow wands. There has been a huge increase in the size of the willow trees alongside the river in the last few years- their predecessor trees were pollarded annually and now the regularly shed smaller branches and more recently larger ones in the winter gales. I have also received reports that upriver thinning of these trees has been done earlier in the autumn in the area adjacent to where the river passes under the Amersham bypass and the branches have fallen in the river.
4. Additional Contributory Factor
Another problem is that there has been no proper street clean since the final leaf fall in early December by CDC's contractors, so drains are additionally blocked by leaves and rubbish.  CDC should recognise this is a critical time for a clean to get us throught the winter. You only have to look at the parking area outside Gilbey's in Market Square to see that the drain is completely blocked there as it is outside the Elephant and Castle. A coordinated Bucks CC and CDC street clean and drains maintenance after the leaf fall and ahead of the winter rainfall in early December would seem like a sensible regime to introduce annually.
5. Conclusion
My conclusion, subject to expert confirmation, is that his is an issue of management and maintenance rather than river flow. In fact the EA website currently reports normal flows on the River Misbourne for this time of year, Quote,
"Misbourne at Missenden Last updated 18:00 on 09/01/2014 Summary The river level at Missenden is 0.26 metres. This measurement was recorded at 18:00 on 09/01/2014. The typical river level range for this location is between 0.04 metres and 0.70 metres."
6. Early Solution and Lead Responsibility Required
The problem is who is the ultimate authority for resolving this on a permanent basis? The EA sort of put their hands up, but have reminded me that strictly this is the responsibility of riparian owners including private owners and Amersham Town Council.  I would suggested an early coordinated meeting between BCC, CDC, ATC , relevant riparian owners and the EA as well as affected residents is urgently needed to put in a single coordinated "Total Place" long-term solution. Currently seems to be a diffusion of responsibility, information and leadership.
One possible permanent solution I would offer, is that once the tunnels and culverts have been cleared, a metal vegetation "catcher" is placed in the river at the SE downriver end near the back of 127 High Street by the owners and Amersham Town Council and this could be cleared from time to time by Council parks staff who maintain Barn Meadow. This would avoid any future blockages in the difficult-to-access river tunnels. The EA indicated to me that normally they would only like to tackle this when flows are lower and it is warmer and I accept at the moment they are in crisis mode with far more acute problems elsewhere in the NW Thames area.
Would one of you suggest who might take this up to get this extended problem resolved so we avoid the problem in the future and particularly for next winter?  Alternatively, if this issue is already being addressed, could it be communicated to us as residents?
CDC's Flooding Information note to residents this week reminds us that it is residents' responsibility to protect their property, but if it is proven that this is an avoidable problem as a result of negligent maintenance elsewhere, then clearly this is not the case.