SimUrba: Urban planning model for a spatial representation of NBS scenario in the Lez demo by 2040

Description

Where a city will be in twenty years determines where a Nature Based Solution can be put and what it will be worth. SimUrba is an urban model that projects the urbanisation of the Lez catchment to 2040 and represents the NBS scenarios of the demonstration site on the resulting land-use map.

The model simulates the spatial development of the urban area under different assumptions about growth and planning policy, and then locates the measures of a strategy within that future fabric. This matters for two reasons. First, the value of a measure depends on what is around it: a retention basin in an area that becomes built-up protects more assets than one in an area that remains agricultural. Second, the feasibility of a measure depends on land availability, which changes as the city grows.

The output is a spatial representation of each scenario, which allows the strategy to be discussed in the terms that planning decisions are actually taken in.

Applications to decision making in the insurance sector

Exposure changes with urbanisation, and a risk appraisal based on today's land use will understate the losses that a measure avoids if the catchment is growing. SimUrba supplies the future exposure map that a forward-looking risk assessment requires, and it shows how the avoided-damage figure from the economic assessment changes when the city is represented as it will be rather than as it is.

Added value of this modelling approach

It connects a hydrological strategy to a planning process. Measures that cannot be located in the future city cannot be implemented, however well they perform in the model, and the spatial representation is what reveals that early.

What decision can be improved with this modelling approach

Where to site measures given expected urban growth; whether a strategy remains effective as the catchment develops; and how to coordinate water risk management with land use planning.