基于GIS的林火蔓延模拟的实现

为定量描述林火行为以辅助扑救决策,利用地理信息系统(GIS)软件建立林火蔓延模拟的空间背景并生成相应数据,运用林火蔓延模型且综合考虑火场地形、气象及可燃物类型等因子,采用点到点的传播方式,用Visual Basic 6.0开发软件,最终实现林火蔓延的动态模拟。模拟的结果表明,在地形条件一定的情况下,林火的初始蔓延速度和风速的大小对林火蔓延有明显的影响,不同的初始蔓延速度会导致不同的蔓延结果,随着初始速度的增大,蔓延面积也相应增加;不同的风速形成的火场面积不同,随着风速的增大,蔓延面积也相应增加,但火场的形状相似;坡向不同,接受阳光的照射不同,温度、湿度、土壤和植被都有差异,一般南坡比北坡更容易燃烧且蔓延速度快;不同的坡位会导致林地内水分含量不同,进而也会影响林火的蔓延速度。图5参12

Realization of a simulation model for forest fire spread

For decision making when fighting forest fires,it is important to quantitatively describe the behavior of a forest fire.Therefore,the purpose of this study was to achieve a dynamic simulation model for the spread of forest fires.Using GIS software,the space background of a simulation for forest fire spread was established and the initial data were originated.The fire spread model contained factors,such as terrain,weather,types of combustible materials,and point to point mode of transmission,while using Visual Basic 6.0.Results indicated that with a given terrain,varying the initial spread rate could cause different spread patterns;also the area consumed by the fire increased with an increasing initial velocity.Different wind speeds resulted in dissimilar sizes for a fire scene.The size of a fire scene increased with wind speed,but the shapes of the scene were similar.The highly effective sample computations,balanced formula load,and perfect disposition increased simulation precision and efficiency.