Peckham Church, London

A flagship contemporary church building on a prominent site along Peckham Road, London.

Scope of Work

Herrington Consulting were tasked with producing a Flood Risk Assessment and Surface Water Management Strategy for the site. Whilst the risk of flooding was deemed low from all sources, the drainage design proved more complex, with the proposed church and associated parking covering nearly the entire site and an existing sewer crossing the site.

Constraints/difficulties overcome as part of the project

Due to the invert level of the proposed sewer connection and the presence of an existing public sewer crossing the development site, it was necessary to keep all of the drainage above or as close to ground level as possible. Consequently, we utilised the flat lower level roof areas as green roofs and then provided permeable paving within the parking areas. We also worked with the LLFA to specify tree crates in the planted areas of the site to provide further SuDS and sustainability benefits.

The solution provided would result in a 99% reduction in discharge rates for the design event when compared to the existing site.

Images courtesy of Turner Jackson Day Associates

Overlap with other consultants

Architects – locations of SuDS, inclusion of green roof

We collaborated with the architects Turner Jackson & Day Associates to ensure that the proposed SuDS did not impact on the movement of people across the site and its intended use, whilst providing SuDS which offered wider sustainability benefits and green spaces.

Peckham Church

Rufus Business Centre, London

This is an example of where a range of services offered by Herrington Consulting were employed on a challenging and exciting development project that had numerous environmental constraints. The scheme included a series of mixed use commercial and residential blocks ranging from 3 to 8 storeys and replaced an existing lower rise commercial building.

Daylight & Sunlight

Our initial involvement in the project was in the very early stages of the design where we worked alongside the architect to develop massing envelopes that were specifically ‘tuned’ to ensure the proposals would not adversely impact upon the daylight and sunlight enjoyed by the neighbouring properties. This was further developed as the design progressed and a detailed assessment was prepared to accompany the planning application.

Transient Overshadowing Study

This assessment also included a transient overshadowing study that allowed the shadows cast by the development to be tracked on an hour-by-hour basis for a range of times throughout the year. This provided a clear indication of any potential overshadowing impacts.

In addition to the impact on neighbours, we also worked with the architects to ensure that all habitable rooms within the development

would benefit from good levels of natural daylight and sunlight.

Solar Glare

The development is adjacent to the railway line and therefore the potential for reflected sunlight from the façades of the buildings to cause reduced visibility or distractions to train drivers was identified at an early stage. To ensure that the proposals would not impact on the safety of the railway a solar glare study was undertaken. This utilised numerical modelling techniques to simulate potential glare instances at a range of assessment locations along the railway line at different times of day. This was repeated throughout the year to identify all potential glare instances, and for each time/location that a potential glare risk was identified, the veiling luminance was calculated. This was then used to assess disability glare from the source.

Flood Risk

The site lies within Flood Zones 2 and 3 of the River Wandle and whilst it was possible to design the scheme such that all living accommodation was raised above the design flood level, the scheme did have potential to displace floodwater, thus increasing the risk of flooding elsewhere. Our role in the design was therefore to ensure that the volume of floodwater displaced was not increased by the scheme.

Using hydraulic modelling, different options were tested and refined. The final design included a floodable void space beneath part of the building, as well as voids beneath a raised landscaped public realm area in the middle of the site.

Medmerry Park

Considerations

From a flood risk perspective, this was an incredibly challenging site with the risk of flooding from the coast being compounded by the risk of fluvial flooding from watercourses that run directly through the site and discharge to the sea. This project drew on the specialist skills of our flood risk consultants, coastal and drainage engineers as well as our in-house numerical modelling resources to identify all of the potential mechanisms of flooding, mitigation measures to reduce risk and a detailed strategy for protecting the site from flooding for the next 100 years.

Numerical Modelling

Nearshore wave climate analysis within the harbour undertaken using Boussinesq modelling, suite of wave overtopping models used, 2D hydrodynamic TUFLOW model used to determine flow paths and new flood gate design.

Coastal Morphology

The shoreline between Selsey Bill and the entrance to Chichester Harbour has been subject to storms and roll-back for centuries and Medmerry in particular has an extensive history of flooding, erosion and breach. The management of coastal flooding along this frontage is therefore intrinsically linked to the future evolution of the shoreline. One of the key elements of this project was therefore to gain an understanding of how the shoreline and in particular the shingle barrier beach will evolve over the next 100 years. The response of the beach to extreme storm events was simulated using numerical models, and in combination with the longer-term predictions of the shoreline evolution, this information was used to understand how the protection provided by the natural beach will change over time.

The outcome

From the outset, our project team engaged with the Environment Agency to ensure that our methodologies and strategic planning for the management of risk at this site were supported. As a result of ongoing consultation, and following the technical validation of our wave and hydraulic modelling, the Environment Agency confirmed that it had no objections to the proposals for the redevelopment of the holiday park.

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Project Category: Flood Risk