Assessing the hydrologic response to wildfires in mountainous regions
This study aims to understand the hydrologic responses to wildfires in mountainous regions at various spatial scales. The Soil and Water Assessment Tool (SWAT) was used to evaluate the hydrologic responses of the upper Cache la Poudre Watershed in Colorado to the 2012 High Park and Hewlett wildfi...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-04-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/22/2527/2018/hess-22-2527-2018.pdf |
| Summary: | This study aims to understand the hydrologic responses to wildfires in
mountainous regions at various spatial scales. The Soil and Water Assessment
Tool (SWAT) was used to evaluate the hydrologic responses of the upper Cache la
Poudre Watershed in Colorado to the 2012 High Park and Hewlett wildfire
events. A baseline SWAT model was established to simulate the hydrology of
the study area between the years 2000 and 2014. A procedure involving land
use and curve number updating was implemented to assess the effects of
wildfires. Application of the proposed procedure provides the ability to
simulate the hydrologic response to wildfires seamlessly through mimicking
the dynamic of the changes due to wildfires. The wildfire effects on curve
numbers were determined comparing the probability distribution of curve
numbers after calibrating the model for pre- and post-wildfire conditions.
Daily calibration and testing of the model produced <q>very good</q> results.
No-wildfire and wildfire scenarios were created and compared to quantify
changes in average annual total runoff volume, water budgets, and full
streamflow statistics at different spatial scales. At the watershed scale,
wildfire conditions showed little impact on the hydrologic responses.
However, a runoff increase up to 75 % was observed between the scenarios in
sub-watersheds with high burn intensity. Generally, higher surface runoff and
decreased subsurface flow were observed under post-wildfire conditions.
Flow duration curves developed for burned sub-watersheds using full
streamflow statistics showed that less frequent streamflows become greater in
magnitude. A linear regression model was developed to assess the relationship
between percent burned area and runoff increase in Cache la Poudre Watershed.
A strong (<i>R</i><sup>2</sup> > 0.8) and significant (<i>p</i> < 0.001) positive correlation was determined between runoff increase and percentage of burned area upstream. This study showed that the effects of wildfires on hydrology of a watershed are scale-dependent. Also, using full streamflow statistics through application of flow duration curves revealed that the wildfires had a higher effect on peak flows, which may increase the risk of flash floods in post-wildfire conditions. |
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| ISSN: | 1027-5606 1607-7938 |