Soil erosion, reservoir lake infill and coastal erosion in the
Mediterranean coast of southern Spain.
Abstract
The combination of vigorous terrain and millenary human action has
produced major changes in vegetation cover, impacting soil losses from
slopes and, consequently, sediment production. Increasing focus in the
management of water resources led to the widespread construction of dams
to generate water flows for iron production, irrigation and to satisfy
the increasing demand of the massive urban development along the Costa
del Sol. To investigate the connection between soil degradation and loss
and river sediment transport retention at a major dam, a first-order
sediment yield prediction was established by using a GIS-based model at
river basin scale. A quantitative validation of model results is
provided by empirical measurements of sedimentation in the main
reservoir lake of La Concepción using D_GPS/Echo sounder combination
and a Remotely Piloted Aircraft compared with pre-construction blue
print topography aimed at documenting spot heights where sediments
accumulated or eroded over 50 years. The significant erodibility that we
have estimated seems matched by potentially high sediment accumulation
rates along selected profiles and spot heights across the bottom of the
reservoir lake. Our study discusses that Mediterranean coastal systems
may no longer stay in the resilience envelope set by a critically
delicate sediment transport balance and without engineering support in
the form of direct sediment feeding to the marine system by the
permanent nourishment works required. Due to soil loss, sediment
entrapment in reservoirs and water management policies, the coastal
protection offered by the natural resilience of the beach and dune
system is no longer recoverable.