Spatial structures of stream and hillslope drainage networks following gully erosion after wildfire

Abstract

The drainage networks of catchment areas burned by wildfire were analysed at several scales. The smallest scale (1-1000 m Scaling laws used to describe large-scale drainage networks could be extrapolated to the small scale but could not describe the smallest scale of drainage structures observed in the hillslope region. The hillslope drainage network appears to have a second-order effect that reduces the number of order 1 and order 2 streams predicted by the large-scale channel structure. This network comprises two spatial patterns of rills with width-to-depth ratios typically less than 10. One pattern is parallel rills draining nearly planar hillslope surfaces, and the other pattern is three to six converging rills draining the critical source area uphill from an order 1 channel head. The magnitude of this critical area depends on infiltration, hillslope roughness and critical shear stress for erosion of sediment, all of which can be substantially altered by wildfire. Order 1 and 2 streams were found to constitute the interface region, which is altered by a disturbance, like wildfire, from subtle unchannelized drainages in unburned catchments to incised drainages. These drainages are characterized by gullies also with width-to-depth ratios typically less than 10 in burned catchments. The regions (hillslope, interface and channel) had different drainage network structures to collect and transfer water and sediment.

The long-term topographic response of a continent adjacent to a hyperextended margin: A case study from Scandinavia

“…where SF is the shape factor, A is the area of the catchment, and L is the catchment maximum length (Moody and Kinner, 2005). Because they take longer to develop, large catchments probably represent long-term conditions better than small ones (Burbank and Anderson, 2001).…”

Comparison of gully erosion estimates using airborne and ground-based LiDAR on Santa Cruz Island, California

“…Previous attempts to quantify gully erosion have usually involved labor-intensive field measurements, such as field tapes, micro profilers, theodolite or total station, and differential GPS methods (Lawler, 1993, Casalí et al, 2006Moody and Kinner, 2006;Nyssen et al, 2006;Rustomji, 2006;Wu et al, 2008). Erosion pins have also been used to measure gully wall retreat (Ireland et al, 1939;Brumbaugh, 1983).…”

Rivers in the Critical Zone

“…The plot shows the mean slope of individual 10 m grid cells for each 0.1 log interval in drainage area. Fourth, the slope of the surface, together with water volume, controls the flow energy available to erode the surface (Moody and Kinner, 2006). The sequence of colluvial, bedrock, and alluvial channel segments is idealized and can alternate downstream.…”