Study On Distribution Characteristics And Risk Grade Division Of Forest Fire In Nanchong City

As a global natural disaster,forest fires not only destroy a large number of forest resources,bring serious impacts on human production and life,but also break the natural ecological balance.In recent years,Nanchong City has increased its efforts in greening and afforestation,and has implemented the development concept of "green mountains and green mountains are golden mountains and silver mountains" with actual actions.The vegetation coverage in this area is increasing year by year,and the type of vegetation in this area is dominated by coniferous forest,which increases the risk of forest fires,but there are relatively few studies on the fire risk zoning in this area.Therefore,it is necessary to carry out forest fire danger zoning research in this area.In this paper,Nanchong City is used as the research area and the "3S" technology is used as the support.Based on the VIIRS 375 m thermal anomaly position vector product(VNP14IMG)dataset,the fire points of 2012-2018 a are extracted,combined with LANDSAT imagery,DEM,and basic geographic data.Using mathematical statistical analysis methods and GIS spatial analysis functions,the distribution characteristics of forest fires in Nanchong City were studied.Eight forest fire disaster hazard factors were selected,and a forest fire risk zoning index system was constructed.The analytic hierarchy process and GIS spatial modeling tools were used to establish Based on the risk zoning model and risk zoning,a forest fire danger zoning map was generated.The forest fire danger zoning map has accurately classified and divided the fire danger in the area,which can play a good early warning role,and has positive significance for reducing the occurrence of forest fires and reducing the losses caused by fires.It provides a scientific reference for the regional fire prevention and control of Nanchong City.The main findings are as follows:(1)According to the statist ical analysis o f VIIRS 375 m fire data products fro m 2012 to 2018,the number o f forest fires in Nanchong fluctuated greatly o n an interannual scale,showing a slowly increasing stat e of fluctuatio n,but not significant;on a seasonal scale,forest fires in Nancho ng It mainly occurs in winter and spring,of which spring is a high-incidence period,and the number o f fire points accounts for 54.59% of the total,followed by wint er,whic h accounts for 38.27%,and summer and autumn are low-incidence periods of forest fires.The fires are mainly concentrated in January,February,March,and April each year,with February,March,and April being the most severe disasters,which is the month of high fire incidence,account ing for 80% of the total fire points.(2)From the point of view of the spatial distribution pattern,the fire po ints in Nanchong are mainly concentrated in the southwest and northeast of Nancho ng.The densit y o f fire po ints is higher in so me areas and less in central areas.In 2012-2018 a,among the 9 districts and count ies under the jurisdict ion o f Nanchong Cit y,high-densit y fires were mainly distributed in Jialing District and Yingshan Count y,account ing for 58% of the total f ire points,of which Jialing District had the largest number,account ing for 33.67 %.In terms of alt itude distribut io n,fire po ints are mainly distributed between 300 m and 400 m above sea level,and the proportion of fire po ints is 61.73%.With the increas e of alt itude,the number of forest fires increases first and then decreases;distribut ion on the slope The fire po int is mainly distributed in areas less than 25 °,and the slope range o f 5 ° to 15 ° is the area where forest fires occur the most,accounti ng for 48% of the total number of fire points,and as the slope increases,Shows a state of high on both sides and low on both sides;in the slope direct ion,the number of fire po ints on the sunny slope is slight ly greater than the number of fire po ints o n the cloudy slope,the proportions are 56.63% and 43.37%,respectively.The fire points are mainly concentrated in coniferous forests,and the number of fire points is 82%.Fit the number o f fire po ints to NDVI functio n.As the NDVI value increases,the nu mber of fire points shows an increasing trend.When the NDVI value reaches the interval o f 0.95-1,the number of fire po ints is the largest,account ing for 23% of the total fire points.From the perspect ive of human activit ies,the fire point is the most w ithin 500 m of the road buffer zone.Wit h the increase o f the buffer zone,the number of fire po ints has been decreasing.The fire po int is the largest at 500-1000 m in the resident ial area buffer zone.As the distance o f the resident ial area buffer zone inc reases,the fire po int increases first and then decreases.When the fire po int is between 200 and 400,the number of fire po ints is the largest,account ing for 58.67% of the total fire po ints.As the populat ion densit y increases,it first increases and the n decreases,and the areas with low and high populat ion densit y almost show Same characterist ics.(3)According to the forest fire risk index,based on the natural breakpo int method,the forest fire danger level of Nanchong cit y is divided into five t ypes of fire risk areas: high risk area,high risk area,medium risk area,low risk area and extremely low risk area.Amo ng them,the area of extremely lo w forest fire danger area is the smallest,accounting for 10.5% of the area of the study area;the area of higher risk area is larger,account ing for 23.6%.(4)The 2012-2018 a remote sensing mo nitoring fire point verificat ion o f fire risk zoning result s showed that 99% of the fire po ints fell in higher risk areas and high risk areas,indicat ing that the forest fire risk zoning model o f this study has good accuracy.