Urban Managed Realignment: Application to the Thames Estuary, London

Abstract

Over the centuries, London has progressively encroached into the tidal Thames River as it has developed into a “World City”. This encroachment has exacerbated the flood risk to new and adjacent land, despite continual upgrading of flood defences. The pressure for further encroachment remains, despite the new threat of human-induced climate change—that is, the combined effect of (1) increased peak river flow in the winter, (2) more intense precipitation events, (3) accelerated sea-level rise, and possibly (4) more severe storms and resulting storm surges. Costly upgrade of defences is inevitable to manage the increased flood risk, and this has caused a re-evaluation of the Thames Estuary's flood defence program. For the first time, managed realignment in urban areas is being considered as a flood management tool. This offers a range of potential benefits including (1) increasing storage for floodwater, (2) improving ecological functioning, (3) improving riverside access for people, and (4) reversing the long-term trend of encroachment into the river. Planned managed realignment can widen the scope for future defence upgrade, but has been limited in urbanised areas. Several projects in London (e.g., Tate Modern and Millennium Dome) have shown that realignment can achieve the benefits described above, which supports the government's recent “Making Space for Water” policy.This study investigates the feasibility of managed realignment in the Thames Estuary. Fragmentation between flood defence and spatial development policies, lack of political support, and riverside encroachment continue to delay urban realignment projects. Successful application will require long-term planning (over decades) that exploits all opportunities for landward realignment offered by redevelopment. With the uncertainties behind climate change and more development in the “Thames Gateway”, further research is needed to understand the contribution of urban realignment to any flood management strategy that may be applied to other coastal urban areas.