Climate change and the increasing costs for water management require a new vision on how to deal with soil subsidence in the Groene Hart. A methodology has been developed for this in the context of a broader study for the Groene Hart as a whole.
This method has been applied in the design research of Vista and Circular Landscapes for the Amstelscheg near Amsterdam. Here, all assignments for the peat area come together on a small scale. Two spatial scenarios have been developed in consultation with regional stakeholders and experts and tested for their effects on subsidence, greenhouse gas emissions, water shortage, water surplus, biodiversity and landscape image.
Image: Current situationPeat meadows with Holstein Friesian cows
Click on map for a lager image
Image above: Scenario Production landscape Wet crops are combined with retention basins in the polder
SCENARIO PRODUCTION LANDSCAPE
In this scenario, the approach to subsidence is used for an accelerated transition from dairy farming to nature-inclusive circular agriculture. The core of this scenario is the large-scale application of underwater drainage in the unearthed peat areas and the construction of retention basins in the adjoining land reclamation sites with residual peat.
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Image below: Scenario Production landscape:Recreational city gardens next to the Amstel river
Image above: Scenario Nature landscapeLand reclamation with peat bog.Swamp forest on higher parts, open water and reed land on lower parts
SCENARIO NATURE LANDSCAPE
Peat recovery and maximum biodiversity are central to this scenario. We save rainwater until the ground level is wetland. Through natural hydrosere will gradually emerge living peat. Living peat is naturally part of the peat landscape, but has almost completely disappeared from the Groene Hart due to extraction and reclamation. Peat formation captures CO2 and will convert soil subsidence into soil increases.
Moreover, it retains a lot of water, which means that both water shortages and large peak discharges will belong to the past. Such an integral transformation requires huge investments and will generate a lot of social resistance. On the other hand, a unique “climate park” can be developed that contributes to the business climate of the Amsterdam Metropolitan Area.
Image below: Scenario Nature landscapePeat development due to retaining rain water
Conclusions and recommendations
Both scenarios differ substantially in their contribution to reducing the subsidence and the water inlet requirement. In the Production Landscape the soil subsidence and associated emissions can be halved, in the Natural Landscape the soil will rise and greenhouse gasses will be actively captured. Both scenarios require substantial investments and have major spatial and social consequences.
To arrive at a well-considered choice, a broader social cost-benefit analysis is needed. At the moment, the Production Scenario appears to have the most support and to best fit in with the meadow bird objective. But it cannot be excluded that in the long term the (phased or partial) transition to a natural landscape will nevertheless be addressed. Both scenarios therefore deserve further investigation and consideration. Part of this may be to set up practical pilots together with landowners and local area parties, preferably on the scale of polder units or related sub-areas.
