| Mountain watersheds are characterized by extreme spatial and temporal variability in processes, making runoff modeling in such settings especially challenging. Fire adds even further variability to runoff dynamics by inducing several highly spatially variable changes in the watershed properties.; The objectives of this research were: (a) to develop a hydrological model for specifically simulating runoff in fire-impacted mountain watersheds, especially in the West Coast of the United States where fire-induced water repellency is relatively common; (b) to conduct a sensitivity analysis of the new model with respect to selected input parameters; (c) to assess the model's ability to represent effects of spatial variations in burn intensity on runoff processes; and (d) to evaluate the accuracy of the model based on comparison of the model simulated hydrographs with recorded hydrographs from a test watershed.; JANSWERS, a new distributed-parameter, event model was developed for modeling runoff under both burned and unburned mountain watershed conditions. The model used several of the core hydrologic equations from ANSWERS, and combined them with newly developed fire-effect representation modules using a new architectural structure.; Utilizing GIS-based data from a test watershed in California to evaluate the sensitivity of JANSWERS to various input parameters, the study found that JANSWERS is sensitive to the significant soil and surface cover parameters that are modified by fire.; With simulations under several hypothetical burn scenarios, the study also found that the model generated runoff hydrographs appeared to have reasonably reflected many of the key runoff processes under both uniformly and differentially burned watershed conditions. Additionally, the model seemed to reflect the substantial rise of runoff for burned conditions under all rainfall-intensity events.; Comparisons of the model generated hydrographs and recorded hydrographs in the test watershed indicated that while JANSWERS outputs seemed to have matched the rising limbs and the peaks of recorded hydrographs, the model would need further refinement for more accurate simulation of the recession limbs of the hydrographs. The study concludes that despite its current limitations, the potential for further development and use of JANSWERS appears to be quite promising. |
