Developing and comparing optimal and empirical land-use models for the development of an urbanized watershed forest in Taiwan

The objective of this study is to demonstrate the utility of optimal spatial models for modeling specific spatial patterns to facilitate rational land-use planning of a watershed in northern Taiwan. Optimization was implemented using simulated annealing in a spatial pattern optimization model (OLPSIM), and developments predicted by the drivers of past land-use changes were modeled with the CLUE-s model. The landscapes simulated by the models were then input to a precipitation-runoff model (the Hydrologic Engineering Center's Hydrologic Modeling System; HEC-HMS) to assess the impact of land-use patterns on runoff in the watershed and sub-watershed scales. The results suggest that the three strategies produced very different landscapes under medium intensity scenarios. Specifically, maximizing the size of forest patches caused deforestation of small forest patches, resulting in a large, complex-shaped, dispersed forest; minimizing forest patch shapes resulted in the dissection of large, complex-shaped forests into smaller, simpler-shaped fragments; and land development based on past trends resulted in the aggregation of urbanized land-use in gentler terrains. The results of hydrological simulations suggest that the three land-use strategies differ less in their total hydrological outputs, but more in their distribution of hydrological outputs across different sub-watersheds. Investigating more spatially explicit hydrologic impacts of urbanization at the sub-basin scale may provide additional information that would help decision-makers evaluate proposed land-use policies more thoroughly.