Emergent Behavior in Slow-Fast Landscape-Climate Dynamics: Evidence from Spatiotemporal Flood Statistics and a Nonlinear Dynamical Model of Coevolution.

Abstract:

Emergent features of landscape-climate coevolution are evaluated on the basis of the sensitivity of floods to annual precipitation in space and time. For that purpose, a spatiotemporal sensitivity analysis is performed at regional scale using data from 804 catchments in Austria from 1976 to 2008. Results show that flood peaks are more responsive to spatial (regional) than to temporal (decadal) variability. Space-wise a 10% increase in precipitation leads to a 23% increase in flood peaks in Austria, whereas timewise a 10% increase in precipitation leads to an increase of just 6% in flood peaks. Catchments from dry lowlands and high wetlands exhibit similarity between the spatial and temporal sensitivities (spatiotemporal symmetry) and low landscape-climate codependence. This suggests that such regions are not coevolving significantly. However, intermediate regions show differences between those sensitivities (symmetry breaks) and higher landscape-climate codependence, suggesting undergoing coevolution. The break of symmetry is considered an emergent behavior of the coupled system. A new coevolution index is then proposed relating spatiotemporal symmetry with relative characteristic celerities. The descriptive assessment of coevolution is complemented by a simple nonlinear dynamical model of landscape-climate coevolution, in which landform evolution processes take place at the millennial scale (slow dynamics), and climate adjusts in years to decades (fast dynamics). Coevolution is expressed by the interplay between slow and fast dynamics, represented, respectively, by spatial and temporal characteristics. The model captures key features of the joint landscape-climate distribution, supporting the descriptive assessment. This paper ultimately brings to light signatures of coevolution that arise from the nonlinear coupling of the landscape-climate system at slow and fast time scales. The presented work builds on Perdigão and Blöschl (2014).

Perdigão, R. A. P., and G. Blöschl (2014), Spatiotemporal flood sensitivity to annual precipitation: Evidence for landscape-climate coevolution, Water Resour. Res., 50, doi:10.1002/2014WR015365.