The effect of rainfall event sequencing on erosion
Jantiene EM BaartmanAJAM Temme, A Veldkamp, VG Jetten, JM Schoorl
Introduction & Objective
Extreme rainfall events contribute disproportionally to total erosion The timing of these events seems to be of importance Climate change predictions (Mediterranean)
● Less total rainfall; but● More intense events
Evaluate the effect of rainfall sequencing on long-term (centennial) erosion
Methods
Methods: LAPSUS landscape evolution model
● Long-term redistribution of sediment
Study area: Prado, SE Spain• ~50 km2
• 435 – 1150 m.a.s.l.• Semi-arid: 250-530 mm/y• High inter-annual variation
Methods
Rainfall data: 1997 – 2006; 9-yr record Repeated 11x to get a 99-yr rainfall timeseries Vary the order of occurrence of rainfall:
• 1997-2006 record repeated 11x• Order of years changed randomly, keeping total rainfall and
frequency the same (50 simulations)• Minimum scenario: 11x lowest year; 11x one-but-lowest year; etc• Maximum scenario: 11x highest year; 11x one-but-highest year; etc
Note: total P is equal in all runs!
Results & Discussion
Results & Discussion
Event sequencing: no linear relation between (high or low) rainfall and (high or low) net erosion
Results & Discussion
Event sequencing: no linear relation between (high or low) rainfall and (high or low) net erosion
Conclusions & Outlook
Non-linear behaviour is evident: ● Non-varying, average annual rainfall as input results
in peaks in simulated net erosion ● Variability in rainfall as input does not necessarily lead
to a corresponding peak in simulated erosion and peaks occur at points in time when no rainfall peak occurs.
What is the cause of this non-linear behaviour?● Change in connectivity?● Next step: analyse the spatial dynamics
Thank you!
Based on:Baartman et al., 2013. Exploring the role of rainfall variability and extreme events in long-term landscape development. Catena 109: 25-38.
Input: effective rainfall
Peff = P that becomes overland flow Determined based on LISEM simulated hydrographs and
Q/P ratios
More extreme events
Inclusion of more extreme events• 10x erosivity of the most extreme event of the 1997-2006 record• Different frequencies of occurrence of such extreme event
Increased erosivity
Land use change scenario
