Project by: Peter Hermens, Jaap van der Salm & Chris van der Zwet, Netherlands
Location: New Orleans, USA
Client: Wageningen University MSc thesis
Landscape infrastructure for urban water management and climate regulation
It has been several years since hurricane Katrina struck the South Louisiana coastline near New Orleans, flooding 80% of the city up to 9’ (3m), and forcing virtually all citizens to evacuate. The historical parts of the city, located on higher grounds, do well and again have population reaching close to pre‐Katrina levels. However large parts of low‐lying suburbs, such as the studied Gentilly and Lakeview neighbourhoods, are still severely damaged and vacant. This research focuses not only on hurricane threats, but takes into account rainflood events, subsidence, the permanent consequence of vegetation loss, vacancy, and the resulting changes in atmosphere of the neighbourhoods. Together they determine the landscape quality. Three main problems are identified: (1) Extreme rain events frustrate the broken storm water system causing interior flood problems up to 2 ft (60cm) during a 1/10 year storm even; (2) Katrina destroyed 70% of the urban canopy, an estimated total amount of 100.000 trees, resulting in a lack of shade during hot summers and a barren and deserted looking suburban landscape; and (3) over 30% of the residential plots in Lakeview and Gentilly are currently unoccupied, causing a perforated urban tissue. This perforated tissue will not heal on its own accord and needs a structural rethinking, but it also offers opportunities for changes in water management. The designers conclude that the current landscape quality is insufficient and will not recover on the basis of existing policies and address these structural problems with an integrated, long-term strategy.
The project proposes a transformation process aimed at a working landscape. This working landscape performs for humans by ensuring a healthy and pleasant living environment, through inclusion of ecological processes. And this working landscape informs humans by inspiring, revealing and triggering the imagination. Part of this transformation is a new strategy regarding water management, advocating a connected water system based on store‐retain‐discharge principles. As such it mitigates rain flood events, offers conditions for native, sustainable vegetation and provides attractive public space.
How it works
The designers start by quantifying the assignment of the water storage, re-vegetation and healing the urban fabric into cubic meters, hectares, amounts of trees, number of empty plots, etc.
Four landscape zones are revealed; Lakeshore, Whispering Winds, Mysterious Woods and Lush Ridge. The original landscapes, together with topography, rate of subsidence and problems with rainwater flooding are used to define boundaries between the different landscape zones of the project area. Within these zones, the original landscapes (e.g. salt marsh, forest swamp, levee forest) are used as inspiration to define vegetation and accent species, building/water ratio and the type of hydrology interventions and forms.
Next, all open space—including the current drainage system—is defined as design space, quantified and divided in anchorpoints (large park and landscape patches), voids (empty plots) and lines (water and road networks). Within this open space, a new landscape framework will be implemented; the spatial basis for addressing the three earlier stated problems.
Following, the framework is mobilized by introducing extensive surface water and green structures of native and storm proof vegetation:
The framework is firstly used to create an interconnected and branched water system with a continuous flow. Raised outfall canals are lowered and floodwalls are removed (1), revealing the water and creating waterfront opportunities. Outfall canals are connected (2) and the water network is intensified by using road medians (3). Extra connections are made by mobilizing empty lots for water connections (4). The continuous flow in the new system helps reduce nuisances from mosquitoes and obtain a high water quality. In Whispering Winds (where most flooding occurs and subsidence rates are highest) more room is reserved for water than in Mysterious Woods. On the higher grounds of Lakeshore and Lush Ridge a vegetated swale system complements the ‘water machine’.
Second, the framework is robustly replanted with an urban forest canopy based on native vegetation regimes that fit the original landscape zones and ecotypes. Empty plots are temporarily used as tree nurseries. By doing so, the neighbourhoods are diversified by vegetation species and tree density, providing shade, climate regulation and a sense of authentic landscape and local identity to each zone.
Third, the framework is used for experienceable performance. Visible water fluctuations inform residents on their landscape identity and engage the local community in understanding natural processes. New Orleans’ large City Park—covering more acres than New York’s Central Park—located in the centre of the study area will function as an anchor point and showcase for the new landscape structure in the neighbourhoods. The park is redesigned as a water machine that can store 852.500 m3 of water during rain events, 26% of the storage assignment. The park, equipped with new water and vegetation structures, boardwalks, bike routes and canoe rental, besides the redesigned golf course and equest farm, clearly demonstrates how an interpretation of the former appearance of the landscape can provide a connection with place and nature, and enrich the character and identity of the city.
When only 20% of the gross available design space is used to create open water, the system—together with City Park’s new lake—can store 89% of the 1/10yr storage assignment.
Three studies show how this landscape looks in the urban context and answer questions on smaller scale levels regarding the strategic allocation of vacant space—voids, plots and street medians of varying size—for the working landscape structure. They show how canals, grass lined swales and retention ponds can be developed in order to not only function well (improving water buffering and urban climate regulation) but also look good; Truly water as an amenity for the great city of New Orleans. According to the designers, this performing and informing landscape will provide the necessary minimal ingredients for the post-Katrina recovery of the area, while attracting new residents that give liveliness and future to the area.