BACA's Vision for Lakeside, Portsmouth.

Following the driest spring since 1956, the Environment Agency urged UK water companies to strengthen supply protection plans. Both flooding and drought result from similar issues—dried, compacted soil can't absorb heavy rainfall, causing surface runoff. This underscores the need for rainwater attenuation in new and existing developments.

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Our practice, commissioned by Portsmouth Council, applied the LifE (Long-term Initiatives for Flood Risk Environments) methodology, developed for Defra, to regenerate a 50-hectare estuarine brownfield site that once housed IBM’s headquarters. Located in Flood Zones 2 and 3 on the Portsmouth Peninsula, about 5 km from the city centre, the former business park now includes The Porsche Centre and Village Hotel Portsmouth.

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BACA’s vision transforms Lakeside into a medium-density, sustainable, flood-resilient community of ~1,500 homes. It centres on repurposing Building 1000 as a landmark residential core, with penthouses and lakeside views. The adjacent lake becomes a community asset, enabling water-based leisure and hosting floating and static homes.

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Housing types are assigned by flood risk:

• Floating homes in flood zone 3b (river course)

• Amphibious homes in flood zones 3a and 2

• Flood-resilient homes in zone 2

• Traditional, retrofittable homes in zone 1

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This zoning reduces flood risk and aligns with urban planning best practices, incorporating active frontages, density goals, and public/private amenity access. Elevated primary roads ensure connectivity during storms.Green and blue infrastructure defines the masterplan. Three “swale corridors” flow from the lake, splitting the site into four zones—business, residential (Building 1000), and two mixed-use quarters. These swales serve as SuDS, landscaped parks, and flood channels. Positioned near the water, they manage runoff and direct it to flood storage zones, creating vibrant green spaces that support recreation and biodiversity.

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By centralising these swale parks, the plan maximizes usable land and improves wayfinding. Water is embraced as a feature, not a threat, enabling natural flood attenuation and resilience to both flood and drought.Minimal hard infrastructure maintains site permeability. Low-carbon homes cluster around shared green areas designed for water management. Walkability and sustainability are key, with EV charging, cycle lanes, and a local shuttle service.

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The Lakeside masterplan exemplifies climate adaptation, merging placemaking with flood mitigation to create a liveable, water-conscious neighbourhood functional in drought and flood alike.