12/00218/FUL - Armscroft Park PDF 393 KB - Democracy ...

Members had explicitly expressed their desire to see the effects of the
proposal on drainage in the area addressed comprehensively when they were
considering the planning brief.
6.4 The proposals would deliver a replacement bridge at a higher level at
Blinkhorns Bridge Lane (to assist the current ‘bottleneck’ effect that can occur
here in times of heavy rainfall), two temporary storage areas adjacent to the
brook for times of high flow, and localised channel widening.
6.5 Development on the Triangle would also have effects on the ecological
interest of the site. The application proposals involve the provision of
enhanced grassland habitat, wetland habitat, tree planting, provision of
different microclimates in the earth mounds, a range of habitats suitable for
invertebrates, and the erection of bird and bat boxes. A new bridge is also
proposed in the park.
6.6 The works are partially on County Council land. The County has no objections
but has mentioned that the works will need to preserve the swale from the
redeveloped St Peter’s School site adjacent (the spoil mounds do not affect
the swale location).
Flooding issues
6.7 The brook and its immediate environs within the park are in Floodzones 2 and
3. The area of Blinkhorns Bridge Lane immediately north of the rail lines is
also Floodzone 2/3. Clearly the flood mitigation works need to take place at
the Brook and ‘flood control infrastructure’ is defined as ‘water compatible
development’ in the NPPF Technical Guidance.
6.8 The proposed works involve the provision of detention areas with a combined
capacity of 5,000 cubic metres. This capacity should be easily sufficient to
cater for the 30l/s additional discharge from the triangle site (detention volume
of 2,592 cubic metres required). It is also understood that the railway culvert
acts as a control on this stretch of the watercourse.
6.9 The flood detention areas are not proposed as permanent water bodies, and it
is anticipated that they would take around 24 hours to drain following a flood
event that fills them.
6.10 The bridge replacement at Blinkhorns Bridge Lane would provide a higher and
more lightweight bridge which, as well as lifting the structure away from the
water and reducing the ‘bottleneck’ effect, also assists in limiting the build up
of debris – which itself can exacerbate flood problems.
6.11 The Environment Agency considers the works to provide benefits that may
reduce the risk of flooding to residents, especially with the removal of the
existing access bridge which is the primary restriction to flow in the locality of
Armscroft Gardens.
6.12 A local resident has raised several issues relating to flood risk. On the issue of
the ‘missing’ part of the project brief – the modelling work was done by Atkins
PT