The effect of Nature Based Willow system deployment at a catchment scale for flood control

Extreme hydro-meteorological events have caused massive devastations in European territories. The rising frequency and severity of hydro-meteorological events such as floods appear to be associated with climate change and land cover change. Flooding can be broadly classified into three types, fluvial flooding, pluvial flooding and coastal flooding. Fluvial flooding occurs when rivers and streams break their banks and water flows out onto the adjacent low-lying areas (the natural floodplains). Many factors are responsible in understanding the impact of rainfall events to fluvial flooding. The factors are size and slope of catchment, permeability of the soil, urbanization and soil compaction, presence of dams upstream to the floodplain and degree to which water can be stored in the dam and the rate of water release.

Pluvial flooding occurs when the amount of precipitation received exceeds the capacity of storm water drainage systems or the capacity of ground to absorb it.

Due to urbanization process, the surface cover of the land alters leading to increasing impervious areas and decreasing infiltration of the soil

The main focus of the research is to understand the effect of willow plantation at a catchment scale for improving pervious areas for flood control. Willow plants have shown high rate of evapotranspiration and improved infiltration. Willow based systems are used to understand the improvement in the rate of evapotranspiration and infiltration in the presence of appropriate climate and representative soil conditions in Ireland.

The willow systems are being monitored in the western, eastern and northern catchments in Ireland which are regulating the evapotranspiration and also the rate of infiltration at a catchment scale. A statistical rainfall runoff model has been deployed to understand the rainfall-runoff relationship. The evapotranspiration has been estimated based on the Penman–Monteith equation, which requires values of mean temperature, wind speed, relative humidity and solar radiation at daily scale. An inter-comparison for rainfall-runoff relationship is made for estimating the percentage change for improvement in runoff in the presence and absence of the willow plantations.