ANGUS WILSON DANIEL MITCHELL

 Region consists mainly of metamorphic rocks  Overlying soils are thin due to high rates of erosion induced by steep topography  Terraces caused by tectonic uplift

 Tacagua formation:  Parallel to the coast and extending 1km inland  Consists of graphitic and epidote schists  San Julián Formation:  Extends to the crest of the Sierra de Avila  Quartz-plagioclase-mica gneiss and feldspar schists  Peña de Mora Formation:  Extends to the crest of the Sierra de Avila  Quartz-mica gneiss

SANDY SOIL WITH WEATHERED GNEISS STEEP EXPOSED SCHIST

 A historical problem first recorded in 1798  Region built on previous debris flow deposits  Slope stability  Strata are daylighting  Shallow depth of root systems  Low cohesive strength – dependant on pore suction  Heavy rainfall  Increased pore water pressure, which reduced the effective stress, resulting in failure

 Non-structural approaches  Influence future developments  Public education  Early warning systems  Structural approaches  Debris check-dams  Debris basins

DOWNSTREAM VIEWDEBRIS REMOVAL

 Discouraging future development  High risk areas already heavily built up  Advanced warning systems  Steep surrounding terrain ▪ Reduced warning time ▪ Limited evacuation routes  Dams and basins  High initial investment and continued maintenance  Good design requires well defined flow paths

Solutions Adopted  Consideration at design stage for new developments ▪ Building orientation ▪ Road alignment  Public education