Response and Recovery of Watersheds to Environmental Change

对人为引起的环境变化的日益关注突出表明，需要更全面地了解关键系统对不断变化的环境条件的性质和反应速度。需要更多知识的关系包括水文系统对流域内土地利用变化的反应。该项目将分析上个世纪格鲁吉亚西南部流域响应的动态，该地区在19世纪中后期发生了迅速的森林砍伐，导致了一个深而复杂的沟壑和峡谷系统。然而，近几十年来，该地区的伐木和农业活动大大减少，径流制度的变化虽然不那么剧烈，但却很重要。该地区的实地工作将为更准确地确定土地利用干扰和河流反应的年代提供信息。山谷填充物和阶地序列的沉积物样本将通过树木年代学和航空摄影分析确定年代。土地使用的变化将通过税务记录和航空照片来确定。从这些调查中获得的数据将与地形和气候数据相关联，使用改进的水文模型。该项目将有助于从理论上和经验上理解促进河流地貌不稳定的条件。它还将有助于对流域特征因人类活动而发生变化时反应和恢复的滞后时间有新的认识。

Increased attention to human-induced environmental change has highlighted the need to understand more completely the nature and rate of responses of critical systems to changing environmental conditions. Among the relationships for which greater knowledge is needed are responses of hydrologic systems to changes in the land uses within drainage basins. This project will analyze the dynamics of watershed response to during the last century in southwestern Georgia, where rapid deforestation occurred in the mid- to late-1800s, leading to a deep, intricate system of gullies and canyons. In recent decades, however, logging and agricultural activity in the area have diminished substantially, causing less dramatic but nonetheless significant changes in runoff regimes. Fieldwork in the area will provide information for more accurate dating of land-use disturbances and fluvial responses. Sediment samples of valley fill and terrace sequences will be dated through dendrochronologic and aerial photographic analyses. Land-use changes will be identified using tax records and aerial photos. Data from these investigations will be related to topographic and climatic data using a modified hydrologic model. This project will contribute to both theoretical and empirical understandings of the conditions that promote fluvial geomorphic instability. It also will contribute to new knowledge about the lag times of response and recovery when watershed characteristics change through human activity.