Doctoral Dissertation Research: Modeling the Impacts of Fire and Post-Fire Succession on Long-Term Streamflow Dynamics in Southern California Chaparral Watersheds

相对较少的科学关注在地中海类型的灌木丛，如加利福尼亚州夏帕拉尔，火灾后植被移除和重新生长的水文影响。少数针对这一问题的研究是在完全或几乎完全烧毁的小型试验性流域中进行的，时间很短。然而，大型丘陵流域的火灾很少烧毁整个流域，而且尚不清楚火灾大小和位置的变化如何影响径流量及其季节变化。因此，这项博士论文研究项目将使用一个基于物理的、空间上显式的计算机模型来模拟南加州两个大型查帕尔流域的径流。多个模型运行随机产生的不同大小和位置的火灾将被用来调查火灾和植被再生对这些流域长期径流动态的影响。将对过去15年收集的卫星数据进行分析，以确定水文模型的植被再生特征。该项目将有助于建立可靠的径流模型，这对于流域的合理管理以及水资源规划、水质预测、洪水缓解和生态系统保护是必要的。火灾对查帕尔流域和其他地中海类型生态系统中的分水岭的景观条件造成了最戏剧性和最反复的变化。大约6%的地球陆地表面被类似于查帕尔植被的灌木丛覆盖。因此，该项目的结果将在南加州的分水岭以外具有水文意义，并将对类似生态系统的研究和流域管理具有重要意义。这项研究还将阐明流域对可能伴随假设的全球变暖而来的火情变化的水文响应。由于该项目采用了从遥感数据获取模型输入的新程序，因此水文建模方法和结果将与其他基于物理的、空间分布的模型的用户相关。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

Relatively little scientific attention has been given to the hydrologic impact of vegetation removal and regrowth following fires in Mediterranean-type shrublands, such as California chaparral. The few studies that have addressed this problem have been carried out over short periods of time in small experimental watersheds that were completely, or nearly completely, burned. Fires in large chaparral watersheds rarely burn the entire watershed,however, and it is not known how variations in fire size and location affect streamflow volumes and their seasonal variations. This doctoral dissertation research project therefore will use a physically based, spatially explicit computer model to simulate streamflow in two large chaparral watersheds in southern California. Multiple model runs with randomly generated fires that vary in size and location will be used to investigate the impacts of fire and vegetation regrowth on long-term streamflow dynamics in these watersheds. Satellite data collected over the past fifteen years will be analyzed to determine vegetation regrowth characteristics for the hydrologic model. This project will contribute toward reliable modeling of streamflow, which is necessary for the sound management of watersheds and for water resources planning, water quality prediction, flood mitigation, and ecosystem preservation. Fires produce the most dramatic and repeated transformation of landscape conditions in chaparral watersheds and watersheds in other Mediterranean-type ecosystems. Approximately six percent of the Earth's terrestrial surface is covered by shrublands similar to chaparral vegetation. The results of this project therefore will have hydrologic relevance beyond watersheds in southern California and will be significant for research and watershed management in similar ecosystems. The study also will shed light on the hydrologic response of watersheds to changes in fire regimes that may accompany hypothesized global warming. Because this project employs novel procedures to obtain model inputs from remotely sensed data, the hydrologic modeling approach and findings will have relevance to users of other physically based, spatially distributed models. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.