Riera de Ribes Extreme Weather flash flood study methodology

'Many places are experiencing an increased risk of river flooding. Design a programme of fieldwork and research to investigate the reasons for this.'

Site 1


1. Look for evidence of past flood(s) – the 1962(?) flood notch and fluting. Discuss importance of the evidence.
2. Talk about the impact of the 1962(?) floods in Barcelona – 1,000 dead - see http://www.rinamed.net/docs/comunic/gama1_final_RAM.pdf  http://www.elpais.com/articulo/cataluna/Valles/recuerda/grandes/inundaciones/1962/elpeputec/20020924elpcat_17/Tes and http://gama.am.ub.es/edrinacas/riscos/impacte.htm
3. Look for evidence of features that increase the flood risk:

• Outside of meander bend (go to top of cliff to view, photograph, sketch).
• Building on floodplain; increased urbanisation - impermeable surface and storm drains. Visit a storm drain.
• Sewage pipes laid underneath the river bed.
• Intensification of land use - the clearance of forest and pasture to grow vines increases the flood risk.
• Steep terrain (second most mountainous country in Europe.
• Mediterranean climate (baked soils, torrential Autumn storms).
• Visit and talk about management features that have been constructed to protect against the flood risk

4. Research tasks

• What rainfall is associated with such a flood event?
• What is the flood return time for such an event? (Worksheet to come).
• Are flood return times shrinking with climate change?
• What are the characteristics of a Mediterranean climate that causes flash flooding?

5. Ask the consolidation question, ' what evidence can you see for an increased risk of flooding at this location'?
6. What fieldwork methods can we use to investigate this increased risk?
7. Conduct the study

Site 2

1. Look for evidence of past flood(s).
2. Look for evidence of features that increase the flood risk:

• Outside of meander bend (photograph, sketch).
• Riera de Jafre joins upstream (see drainage basin map)
• Building on floodplain; increased urbanisation - impermeable surface and storm drains. Visit a storm drain.
• Visit and talk about management features that have been constructed to protect against the flood risk
• Multi-arched bridges act as dams. Note the current construction work to reduce the bridge flood risk.
• Campsites have no protection or warning. Assess the campsite flood risk.
• River channels should be kept clear of vegetation by law.

5. Ask the question, ' what evidence can you see for an increased risk of flooding at this location'?
6. Ask the question, 'what historical evidence exists that farmers avoided high flood risk areas for their crops?' Visit the field boundary and measure the height of the field.
7. What fieldwork methods can we use to investigate this increased risk?
8. Identify actual spot heights on the map and explain how these can be used to investigate the flood risk
9. Conduct the study, at bank full (no flood notch exists)

Riera de Lluc/Bisbal study flash flood management

'Examine the success of strategies used to manage one type of extreme weather event' or 'Describe the methods used to manage an extreme weather event and comment on their effectiveness'.