Rob Halpin (M Sc)

M.Sc. Environmental Science (2017-2018)

Fieldwork in progress. Photo taken during image capture stage of DEM creation in Gurteenflugh, Co. Cork.

TITLE: Natural Water Retention: Opportunity mapping and flow modelling in the upper Lee Catchment, Cork

Abstract:

Due to an increase in urban and agricultural expansion over recent decades, there has been a decrease in permeability in formerly natural landscapes, as well as a reduction of natural floodplain area. This has, therefore, altered the natural ability of many catchments to attenuate flood waters. Furthermore, traditional flood defence schemes are often deemed not to be cost effective in smaller communities. Finally, under climate change scenarios, peak flows in fluvial channels are expected to increase in the range of 20-30% by the end of the century in Ireland, making hard-engineered solutions to flood prevention (such as the construction of structural defences and dredging of river channels) unsustainable.

This research project, therefore, explores the alternative flood management strategy of Natural Water Retention [NWR] in the region of Ballingeary, Co. Cork, where numerous flooding events have occurred over the past decade. Suitability of the area to NWR measures was carried out through the use of opportunity mapping and basic hydrological modelling (GIS). In total, an area of ~64,000 m2 which could be utilised as water storage areas were identified within the 1.4km2 study area. Furthermore, a total area of ~53,400 m2 was identified as suitable to riparian buffer extensions, as well as several areas suitable to both Engineered Log Jams [ELJs] and peatland drain blocks.

A selection of these suggested Runoff Attenuation Features [RAFs] were subsequently modelled to ascertain their impacts on flow both within the catchment, and further downstream. Although further analysis of proposed RAFs is required (through the construction of pilot structures), it is suggested that NWR could provide viable flood protection during smaller fluvial events in the area of Ballingeary village.

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