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NRW_DS121714

Teitl Amgen

• SCCAN Urban Green Infrastructure: Demand for Urban Greenspace - Risk of Pluvial Flooding

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To create this dataset, a Digital Surface Model (DSM) for Wales was derived from the NextMap Digital Terrain Model (DTM) and OS MasterMap data. Average building and feature heights were assigned to relevant MasterMap features and added to the DTM to produce the DSM.

The hydrology of the resulting DSM was analysed using SCIMAP (Durham University, 2016). Although SCIMAP was originally developed to model erosion risk, one of its intermediate outputs, the Network Index (connectivity), can also be used to indicate potential urban pluvial flood risk when applied to a DSM. The Network Index describes the likelihood of a parcel of land transferring material, in this case water, to another location. Areas with particularly high Network Index values were identified as being at greater risk of pluvial flooding.

To distinguish between areas susceptible to standing water and those susceptible to overland flow, slope data were used. Areas with slopes of less than 3° were classified as being at risk of standing water accumulation, while areas with steeper slopes were classified as being at risk of overland flow.

Demand for intervention was assessed using population density and the Welsh Index of Multiple Deprivation (WIMD). Population density, derived from census data, was classified into five categories using Jenks Natural Breaks. The two highest population density classes were assigned high priority, while the middle class was assigned moderate priority. WIMD data were classified using the categories published on the WIMD website. The two most deprived categories (ranks 1 to 382) were assigned high priority, while the next category (ranks 383 to 573) was assigned moderate priority.

This dataset was produced for NRW by Environment Systems Ltd.

Gwybodaeth ychwanegol

Data gaps and limitations: For urban areas, the distinction between streets and buildings becomes increasingly important. As a result, a resolution finer than the 10 m pixel size used for the strategic-scale mapping undertaken for this project may be desirable. Urban drainage systems have not been considered in this mapping, which may result in the overestimation of standing water risk in some areas.

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2018-04-01

 

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