Using modified Soil Conservation Service curve number method to simulate the role of forest in flood control in the upper reach of the Tingjiang River in China

To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based on the Soil Conservation Service curve number(SCS-CN) method. Parameters of the model were selected and determined according to the comprehensive analysis of model evaluation indexes. The first simulation of forest reconstruction scenario,namely a coniferous forest covering 59.35km^2 is replaced by a broad-leaved forest showed no significant impact on the flood reduction in the URTR. The second simulation was added with 61.75km^2 bamboo forest replaced by broad-leaved forest,the reduction of flood peak discharge and flood volume could be improved significantly. Specifically,flood peak discharge of 10-year return period event was reduced to 7-year event,and the reduction rate of small flood was 21%-28%. Moreover,the flood volume was reduced by 9%-14% and 18%-35% for moderate floods and small floods,respectively. The resultssuggest that the bamboo forest reconstruction is an effective control solution for small to moderate flood in the URTR,the effect of forest conversion on flood volume is increasingly reduced as the rainfall amount increases to more extreme magnitude. Using a hydrological model with scenarios analysis is an effective simulation approach in investigating the relationship between forest type change and flood control. This method would provide reliable support for flood control and disaster mitigation in mountainous cities.

An Approach to Environmental Planning and Sustainable Management of Watersheds and Municipalities in Southeastern Brazil

Diagnosis of fragmentation and landscape sustainability conditions are essential to environmental planning and sustainable management of natural resources. Land use spatial patterns and landscape structural indexes (landscape metrics, Urbanity Index— UI, and Landscape Vulnerability Index—LVI) have been proposed to assess biodiversity conservation and ecological sustainability, provided by impact of land use at Middle Mogi Gua&#231u watershed and its seventeen municipalities, in 2009. Land use typologies and structural indexes values were obtained based on screen digitizing of LandSat-5 imagery, for 2009. Cluster analysis and Permutational Multivariate Analysis of Variance were used to test the null hypothesis of equal degrees of fragmentation and sustainability conditions among municipalities in 2009, respectively. Land use spatial pattern showed a predominantly human occupation for watershed and its municipalities, with agricultural use as the main pressure factor. Municipalities were aggregated into three clusters related to forest fragmentation: one categorized by fifteen municipalities;the second cluster (municipality of Luiz Ant&#244nio) showing the best condition, and the third group (municipality of Araraquara) with extreme fragmentation condition. Landscape metrics related with shape, size, and core areas fragments intensify edge effects, and increase habitat isolation. The watershed showed a low naturalness and an intermediate degree of vulnerability. Ecological sustainability was different among municipalities (α = 0.05, F = 32.65 and p = 0.002), with two municipalities (Analandia and Luiz Ant&#244nio) presenting the best conditions. The most committed condition was observed, in municipalities of Rinc&#227o and Guatapará. For conservation policies to be effective must focus on the creation of ecological corridors around legally protected areas, besides creation of new legal reserves, with purpose to improve biodiversity conservation and ecological sustainability of Middle Mogi Gua&#231u watershed and its municipalities.