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Biodisturbance and Ephemeral Channels

picture of beetle-killed tree
Beetle-killed tree in
Rocky Mountain
National Park, CO
(Photo by G. David)

The effect of insects and wind on ephemeral channels depends on the elevation and aspect, therefore the expected influence of biodisturbance on ephemeral channels is split by vegetation.

Lower Ecotone and Lower Montane – The potential increase in runoff from decreased amounts of interception and transpiration from trees is more likely to affect this ephemeral channel domain. These basins are smaller and therefore it is more likely that 100% of the trees have been infected by beetle, causing a larger amount of water to enter into the ephemeral channels, increasing erosion and channel incision.

Fire and Ephemeral Channels

(Information compiled by G. David)

Picture of ephemeral channel
Ephemeral Channel
in Poudre Basin
(Photo by G. David)

The expected response of ephemeral channels to fire depends largely on vegetation zones, fire severity and rainfall intensity. Moody and Martin (2001) found that most of the sediment after a fire came from the headwaters of a drainage basin and was subsequently stored in the higher order parts of the basin in flood plain deposits, alluvial fans and channel fill. Therefore, ephemeral channels are most likely to be infilled following a fire, and after vegetative re-growth has occurred on the hillslopes the channels may eventually be incised and the sediment moved further downstream.

Historically, the lower ecotone and lower montane had low to moderate severity fires. Higher severity fires are expected after years of fire suppression in these zones. Intense convective storms are expected in the lower elevations, therefore a high severity fire followed by a few severe storms would lead to increased erosion on these slopes, particularly on north-facing slopes (Moody and Martin, 2001). Fires are predicted to have the largest impact on this process domain.


Click a link below to learn about the influence of hillslopes on each process domain:

Colluvial Hollows Ephemeral Channels Glaciated Confined Glaciated Partially Confined Glaciated Unconfined Unglaciated Confined Unglaciated Partially Confined Unglaciated Unconfined
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