Tuesday, June 1, 2010
GIS-based tools to link climate change to river systems
The topography and geology of a basin provide the spatial template that sets the location of different process domains, determining, for example, where landslides occur, or where valley-floor meadows may form. The climate determines the number and magnitude of events that drive temporal and spatial variability over that spatial template: fires and disease alter vegetation cover, storms drive erosion and mass wasting, floods move material downstream. River channels are the communication links: what happens in the uplands is manifest in the lowlands via signals that propagate through the river network. Storm hydrographs vary with position dependent on upstream basin characteristics. Turbidity and sediment load vary with upstream erosional and mass wasting events. The organisms for which a river system is home perceive these events in terms of temporal and spatial variations in habitat. The resultant patterns in habitat abundance and variability may be important drivers of biodiversity and population dynamics. We have or can acquire data to characterize many of these process interactions; we know which erosional processes are active where, we can divide a river network into distinct stream and response types, we can characterize storm, flood, and fire sequences in terms of frequency and intensity, and – with spatially and temporally referenced data – we can tie all these factors together. And once we’ve tied them together, we can assess the likely consequences of a change in the system, a change in frequency of events, which gives us a way to assess the potential impacts of climate change. This “we” I refer to is not just me and my buddies; it is everyone involved in research on river systems. The trick is not only to tie process interactions together conceptually and computationally, but also to link disparate research efforts and data sets. Collaborative and data-sharing opportunities created by development of the internet have motivated a variety of such endeavors, our contribution to which is NetMap (www.netmaptools.org), which offers a geomorphic view of river systems, tempered by interactions with fish biologists, foresters, and others working to figure out how to best manage watershed resources. NetMap provides a common data structure for linking diverse data and model types. I’ll describe what it is, what it is intended to become, and how to use it.