Ranelagh Sailing Club
Concerns have also been expressed in relation to the effect that the proposals would be likely to have upon sailing along this stretch of this river. These concerns relate primarily to the impact which the increased height and length and proposed siting of the buildings would have upon wind conditions. Objectors contend that the new stadium would create a larger area of obstruction to the wind than at present and would make sailing possible on even fewer occasions than at present. They also contend that this could result in the closure of two long established sailing clubs and in the cessation of races on this stretch of the river.
10.19 As was the case when the 1994 applications were considered, the analysis of the likely impact of the proposed stadium development on sailing on this stretch of the Thames has proved most problematic. The ability to sail on this stretch of the Thames (between Putney and Hammersmith) is already restricted by the variable wind and tidal conditions, further complicated by their interaction with natural and man-made obstructions on both banks.
10.20 It is generally only safe and practical to sail on a rising tide in the hour to two hours immediately preceding high water. The water level is too low at low tide for keels to clear the riverbed and for sails to be lifted up by the water level into the wind. Sailing as the tide ebbs is dangerous because of the strong current – the river flows downstream at 3½ knots in the middle of the river. The depth of the river rises by about 4 metres during the period when sailing is practical. Sailing conditions gradually improve as races progress on the rising tide as boats can sail higher relative to riverside obstructions to windflow. The nature of sailing vessels able to cope with the irregular wind conditions and tidal water movements is that they must be small lightweight craft which readily tip over. The sailing conditions can be very challenging particularly in lighter winds and are therefore attractive to the most accomplished sailors. The conditions are generally less suitable for inexperienced sailors unless they are accompanied.
10.22 The tidal cycle and the need to sail in daylight mean that there are between 72 and 90 races each year, usually every weekend in the summer, and a little less frequently in the winter. The Ranelagh Sailing Club’s ability to race to International Yachting competition rules requires a fixed course to be planned in advance and marked out, involving up to 4 laps between Putney and Hammersmith. For a race to be viable and worth competitors at this level bothering to participate, it is necessary to be able to sail upstream (with the tide) as far as Crabtree Drawdock and downstream (against the rising tide) past the football ground to complete each lap.
10.23 To be able to sail against the flow of the tide, boats must either hug the Fulham or Surrey banks, where the tidal flow is slowed by the river edge. Sailors heading south towards the football ground have to elect which bank to use in accordance with the wind conditions. (Sailing upstream on the rising tide is not a problem as boats are carried past the football ground by the current).
10.24 The sailor’s skill, knowledge of the waters and judgement lead him or her to balance the effects of stronger tidal flow resistance further out in the river, with less reliable and unpredictable wind conditions due to obstructions on the two riverbanks.
10.25 When the wind blows from the north or south, the existing football ground presents no obstacle to wind flows on the river. When the wind blows from the east, the "wake" caused by the Eric Miller stand on the river edge forces sailors to hug the Surrey bank. Even with the proposed development’s increase in size and its effect on the wind, it is accepted by all parties that wind conditions would have stabilised sufficiently on the opposite side of the river to allow sailing downstream on the Surrey bank to continue, although conditions might become harder due to reduced wind speed and increased turbulence.
10.26 The real problem, and one which your officers and their consultants acknowledge and which has not been addressed fully by the applicants’ consultants, is the difficulty in sailing downstream in the prevailing westerly/south-westerly wind conditions. Owing to existing natural and man-made obstructions on the Surrey bank and the stronger tidal flows on the outside of the bend in the river it is not normally possible to sail downstream along that side of the river in a westerly wind. The Fulham side has to be used. As the wind blows across the river towards the football ground, a mass of air is held back by the Eric Miller stand with turbulent conditions at its edges, over and around which the wind blows.
10.27 Wind direction can suddenly reverse and vary dramatically with sail height within the unreliable "recirculating" zone. This "linear bubble" or zone of air is not sufficiently stable to be measured or modelled accurately due to the short term variability of the wind’s precise speed and direction (gusts and lulls), the changing height of the water (and consequently the vertical position of obstructing structures on the river bank) and the changing shape and permeability of various features along the river edge.
10.28 attempts by consultants to monitor these extremely challenging wind conditions and measure accurately what is happening now (let alone what may happen if the development goes ahead) have failed to produce reliable results. At the Public Inquiry in 1996 into the 1994 proposals (which the Ranelagh Club strongly objected to), evidence was produced by Watermans on behalf of the applicants based on a computer model of predicted air movement in this zone of turbulent air. The sailing club’s consultants argued that this was seriously flawed and that it was commonly known that down-wind obstructions caused turbulence up-wind of an obstruction for a distance of five times the height of the obstruction. The Council’s present consultants, BMT, do not agree with this and would only expect an upwind recirculation zone to extend, on average, by less than twice the height of the obstruction.
10.29 The sailing clubs contend that the increased height of the proposed development would extend the zone of turbulent air substantially further out into the river, something which was contradicted by the applicants’ computer model. The Inquiry Inspector commented on this subject as follows:
10.30 At present, sailing downstream past the Eric Miller stand in a westerly wind is possible by skilled yachtsmen familiar with local conditions who try to sail along the edge of the region of turbulent and unreliable air (the recirculating zone), avoiding going out too far into the adverse tidal flow. Strong cross-winds penetrating either end of the football ground (between the Eric Miller stand and the Hammersmith end and Putney end stand/terraces) give two additional opportunities for experienced sailors to exploit. Accordingly, this difficult stretch of water can be navigated, although many still fail through bad luck with the timing of gusts inside the unreliable, recirculating zone. Races are of course won and lost on sailors’ ability to cope with such challenging conditions as well as luck with short term changes in air movements.
10.31 Referring again to the previous Inquiry, the Inspector concluded as follows on the effects of the up-wind recirculating or turbulent zone:
10.32 These remarks related to the anticipated impact of the development proposed within the quashed planning permission, which would have increased the height of the obstruction at eaves height by between 1.5 and 4 metres more than the existing Eric Miller stand (compared to an extra 6 metres now proposed). The Eric Miller stand is approximately 7 metres inland from the existing river wall. The previously proposed development would have been 5 metres closer to the top of the river wall than the Eric Miller stand whereas the current proposals would extend beyond the top of the existing river wall by approximately 4 metres at the centre of the site.
10.33 Notwithstanding evidence given to the last Inquiry that an experienced sailor "would easily be able to sail past the site" in average sailing conditions, and the Inspector’s apparent acceptance of this, the Ranelagh Club continues to assert that the conditions here are already marginal and on the limits of what can be tolerated. It maintains that , if conditions became any worse, sailing south past the football ground in prevailing westerly wind conditions would become so difficult as to be no longer practicable at least not for the club’s main purpose of top class racing.
10.34 The proposed development would worsen the existing conditions substantially through a combination of factors:
10.36 The new development would thus produce an obstacle to the wind some 2½ times greater than the existing riverside stand and be closer to the river. In prevailing westerly wind conditions, this would cause the unpredictable recirculating zone of unstable and turbulent air (around which the wind would be more likely to flow more predictably), to increase in all three dimensions (height, length and width) such that it would be likely to present unreliable and difficult conditions for sailing in a larger stretch of river. efforts to measure accurately this likely effect have proved beyond the applicants and their consultants.
10.37 Council officers and their consultants have concluded that the applicant’s consultants’ studies were flawed in that inadequate measurements were taken using unreliable methods given the complex circumstances of tidal movement and changing water levels. Consequently, they have discussed the existing conditions in depth with experienced members of the Ranelagh Sailing Club, as well as with the applicant’s consultants. They have concluded as follows.
10.38 In average wind conditions, assuming a prevailing westerly wind, it is accepted that the existing conditions for sailing downstream past the site would be likely to become significantly worse. It does not appear possible to say conclusively what air movements would occur at different river heights within the unpredictable recirculating zone of turbulent or unstable air, but it seems certain that this zone would extend over a greater area of river on the Fulham side. It would stretch further up and downstream and further out into the river than it does now. Accordingly sailing conditions would be substantially changed.
10.39 It is considered likely that this area of river might not be readily navigable by sailors during prevailing wind conditions depending on the strength of the wind on a given day, but this cannot be said with any certainty. The Council’s consultants BMT estimate that the up-wind recirculating zone could, at worst, extend a maximum of 44 metres out into the river (compared to an estimated 15 metres now).
10.40 But with stronger winds, sailing further out might still be viable as might sailing within parts of the recirculating zone itself. Strong winds would allow sailing in the centre of the river against the incoming tide. However officers conclude that this would be difficult in "normal" wind conditions and impossible in light winds, when sailing is always difficult. It might or might not become impractical to sail downstream past the stadium. All that is known is that the experienced sailors who use this water appear fearful that the conditions would worsen to an extent that would make organising and holding races here non-viable.
10.41 representatives of the Ranelagh Sailing Club say that they lost many members when the Eric Miller stand itself was constructed because several people were unable to cope with the more challenging conditions. The course has shrunk over time with building development, including most particularly riverside flats in LB Richmond (on the prevailing windward side). They are of the opinion that the possible (in their view probable) inability to sail past the proposed development in normal wind conditions would mean that they would no longer be able to organise race meetings. Thus they fear that their sailing would be rendered impractical on the 70% of days when the wind blows in the prevailing westerly direction. This would mean a 70% chance of having to cancel any weekend race due to uncertainty in advance of the likely wind direction. This would in effect prevent organised racing altogether and cause the shrinkage or closure of the club.
10.43 Officers accept that the representations of the sailing clubs have a degree of force. No certainty can exist, however, given the uncertain conditions which would prevail close to the stadium, particularly inside the extended recirculating zone of turbulent and unreliable air, if the development takes place.
10.47 Firstly, this situation would arise from the development’s adding to the cumulative impact of natural and man-made barriers to air flow across the river banks. If the flood relief wall, reservoir banking, line of trees and various buildings did not exist on the Surrey bank opposite the application site, then sailing south in a westerly wind could be feasible on the Surrey bank. Riverside building development in Richmond has apparently already shortened the length of the race course to the north of the application site which can no longer approach Hammersmith Bridge as it once did.
10.48 Secondly, if the Ranelagh Sailing Club is right then it follows that any development of the application site which presented a materially larger obstruction to wind flow than does the existing riverside stand would be likely to carry a similar risk to the the activities of Ranelagh Sailing Club, including, in officers’ opinion, the development granted permission following a Public Inquiry which thoroughly examined this issue, amongst others, in 1996,
10.49 Officers consider that it is material to the consideration of these applications, in the context of the sailing issues, that the clubs’ contention is that conditions are already so marginal that any significant increase in the bulk of the built form, over that presented by the Eric Miller Stand, would put an end to Ranelagh Sailing Club’s activities. Officers consider that there is a clear need for redevelopment of the application site. The Eric Miller Stand presents an eyesore overlooking this stretch of the river, and no river walk will be provided without redevelopment.
10.50 It is also recognised that the improvement of sporting facilities and the creation of a modern day stadium is the most befitting form of redevelopment of the site. If proposals were brought for any redevelopment for such a purpose, coupled with the provision of a river walk, they would be virtually guaranteed to come forward in a form which would have similar potential ramifications for sailing as those threatened by the current scheme.
10.51 In summary officers consider that the possible and likely consequences for sailing along this stretch of the river are a significant material factor to be weighed in the balance in consideration of these applications. These consequences should be weighed against the perceived need to redevelop this site and placed in the balance, together with other relevant considerations, against the benefits arising from the development of the site in the manner proposed in these applications.