SINATRA: Susceptibility of catchments to INTense RAinfall and flooding

Project SINATRA responded to the NERC call for research on flooding from intense rainfall (FFIR) with a programme designed to advance general scientific understanding of the processes determining the probability, incidence, and impacts of FFIR.

Such extreme rainfall events may only last for a few hours at most, but can generate terrifying and destructive floods. Their impact can be affected by a wide range factors (or processes) such as:

• the location and intensity of the rainfall
• the shape and steepness of the catchment it falls on
• how much sediment is moved by the water
• the vulnerability of the communities in the flood's path

Furthermore, by their nature, FFIR are rapid. This makes it very difficult for researchers to 'capture' measurements during events. The complexity, speed, and lack of field measurements on FFIR make it difficult to create computer models to predict flooding, and we are often uncertain about their accuracy.

To address these issues, NERC launched the FFIR research programme. It aims to reduce the risks from surface water and flash floods by improving our identification and prediction of the meteorological (weather), hydrological (flooding) and hydro-morphological (sediment and debris moved by floods) processes that lead to FFIR.

A major requirement of the programme is identifying how particular catchments may be vulnerable to FFIR, due to factors such as catchment area, shape, geology and soil type, as well as land use. The catchments most susceptible to FFIR are often small and ungauged.

Project SINATRA will addressed these issues in three stages:

1. Increasing our understanding of what factors cause FFIR and gathering new, high resolution measurements of FFIR;
2. Using this new understanding and data to improve models of FFIR so we can predict where they may happen;
3. Use these new findings and predictions to provide the Environment Agency and other professionals with information and software they can use to manage FFIR, reducing their damage and impact to communities.

Aims of the project:

1. enhance scientific understanding of the processes controlling FFIR, by:
• assembling an archive of past FFIR events in Britain and their impacts, as a prerequisite for improving our ability to predict future occurrences of FFIR
• making real time observations of flooding during flood events as well as post-event surveys and historical event reconstruction, using fieldwork and crowd-sourcing methods
• characterising the physical drivers for UK summer flooding events by identifying the large-scale atmospheric conditions associated with FFIR events, and linking them to catchment type
2. develop improved computer modelling capability to predict FFIR processes, by:
• employing an integrated catchment/urban scale modelling approach to FFIR at high spatial and temporal scales, modelling rapid catchment response to flash floods and their impacts in urban areas
• scaling up to larger catchments by improving the representation of fast riverine and surface water flooding and hydromorphic change (including debris flow) in regional scale models of FFIR
• improving the representation of FFIR in the JULES land surface model by integrating river routing and fast runoff processes, and performing assimilation of soil moisture and river discharge into the model run
3. translate these improvements in science into practical tools to inform the public more effectively, by:
• developing tools to enable prediction of future FFIR impacts to support the Flood Forecasting Centre in issuing new 'impacts-based' warnings about their occurrence
• developing a FFIR analysis tool to assess risks associated with rare events in complex situations involving incomplete knowledge, analogous to those developed for safety assessment in radioactive waste management.

In so doing, SINATRA achieved NERC's science goals for the FFIR programme.