Judul: Forecasting Land Use Change and the Impact on Water Yield at Watershed Scale
Abstrak: One of the most important issues in watershed management is the use of land, especially in the upstream catchment area. People effort to fulfill their ends meet can cause land conversion. As a result of the land conversion, the Cisadane River condition seems quite apprehensive in the last two decades. Environmental degradation in Cisadane watershed in both the upstream and downstream has a heavy impact to the availability of water resources in Cisadane River. In relation to this fact, an in-depth study on land use change in Upstream Cisadane Watersheds and its dynamics need to be conducted. Particularly, the impact of land use change on water yield. This research purpose is to forecast the future of land use changes (using CLUE-S) and assess the impact of the predicted land use changes on water yield in Upstream Cisadane Watershed (using HEC-HMS). This research was conducted in Upstream Cisadane Watershed – Bogor. The study area is Upstream Cisadane Watershed with outlet of watershed in Empang, which located in both Bogor Regency and Bogor Municipality. Geographically, it is located between 6036’26.05” – 6047’08.49” South Latitude and 106044’30.27” – 106056’36.76” east longitude. Four scenarios are developed based on land use demand (population growth) and area restriction (spatial policy). The scenarios presented are not necessary the most realistic, but are made in such a way that they provide information on the functioning of the model. Binomial logistic regression is used to examine the relation between land use and possible driving factor. The result of this analysis are coefficient values that shows the contribution of each driving factor to land use change. ROC (Relative Operating Characteristics) is a method to measure the goodness of the statistical model. The probability of each land use resulted from logistic regression is compared to the real land use map to calculate the equal category of each grid cell between those maps. This method will depict the capability of regression equation to represent land use characteristics. The goodness of the statistical measurement revealed that ROC values for urban water area, grassland area, estate area, settlement area and forest area were 0.903, 0.701, 0.780, 0.813 and 0.994, which indicated that the probability of land uses built from these models were capable to represent land use changes and empirical analysis by using logistic regression method was satisfactory to examine the relationship between driving factors and land use change in study area. Through model validation process shows that overall accuracy and Kappa accuracy for land use simulation are 90.83 % and 86.00 % or categorized as fit. It indicates that the driving factors have a good capability to explain land use pattern in study area and it can be used to predict future land use pattern. According to the change detection for the land use classification year 1991, simulated year 2000, year 2010, year 2020 and year 2030, it can be seen that settlement, forest and grassland area are increasing over time, whereas estate tend to decrease and water remains constant. Based on the findings, settlement area were significantly increase during the period 1991-2009 and causing
Keyword: Bogor Agricultural University (IPB)