Coupled Human and Natural Systems: Testing the Impact of Agricultural Terraces on Landscape Evolution
Humans alter natural geomorphic systems by modifying terrain morphology and through on-going actions that change patterns of sediment erosion, transport, and deposition. Long-term interactions between humans and the environment can be examined using numerical modeling. Human modifications of the landscape such as land cover change and agricultural tillage have been implemented within some landscape evolution models, yet little effort has been made to incorporate agricultural terraces. Terraces of various forms have been constructed for millennia in the Mediterranean, Southeast Asia, and South America; in those regions some terraces have undergone cycles of use, abandonment, and reuse. Current implementations of terraces in existing models are as static objects that uniformly impact landscape evolution, yet empirical studies have shown that terrace impact depends upon whether they are maintained or abandoned. We previously tested a simple terrace model that included a single terrace wall on a synthetic hillside with 20% slope for the impacts of maintenance and abandonment. In this research we modify the terrace model to include a wider variety of terrace forms and couple it with a landscape evolution model to test the extent terraced terrain morphology is related to terrace form. We also test how landscape evolution, after abandonment of terraced fields, differs based on length of time the terraces were maintained. We argue that construction and maintenance of terraces has a significant impact on the spatial patterning of sediment erosion and deposition and thus landscape evolution modeling of terraced terrain requires coupling with a dynamic model of terrace use.