| It has been one of the hot topics concerning global change that climate change and land use change act synergistically,which increases the frequency of extreme weather and changes the characteristics of regional landscape patterns.In addition,changes in landscape patterns,such as substrate and vegetation cover,can impose an influence on regional landscape ecological risk by changing flooding characteristic values.Therefore,it provides fresh ideas for regional sustainable development and flood control and disaster mitigation by analyzing flood ecological risk from the perspective of landscape ecology,which is helpful for giving full play to the positive ecological effect of landscape.Taking the Liuyang River Basin(LRB)as an example,in this paper,the processes and factors of landscape pattern in the LRB are discussed by analyzing the data of land use,DEM,soil and hydrometeorology.Then,with the use of the HEC-HMS model,the LRB hydrology Simulation system is constructed to study the corresponding relationships between the characteristic values of floods(flood volume&flood peak)and landscape pattern indices of different landscapes.Furthermore,the flood ecological risk(flood-landscape ecological risk)index based on the landscape pattern is constructed,and the spatial and temporal changes of the whole basin risk were analyzed by using the spatial analysis method.The details and conclusions are as follows:(1)Through the analysis of landscape pattern in the LRB from 1996 to 2019,it is concluded that five types of land use in the LRB have changed to varying degrees.Over the study period,changes in cultivated land and forest land have always been dominant in the landscape pattern of the LRB,with more and more land for building under the influence of urbanization and human activities.With the implementation of various ecological protection policies such as returning farmland to forests,the landscape is becoming more diversified and balanced,which makes it less vulnerable to interference because it enjoys a more stable ecosystem.(2)The flood characteristic values of each sub-basin of the LRB are extracted,and the flood-landscape response index is constructed.In this paper,19 floods with different characteristics in the LRB from 1985 to 2019 are selected to construct the HEC-HMS hydrological model,among which 12 are used for parameter calibration and 7 are used for model verification.The results show that the average Nash efficiency coefficient of the selected rate period is 0.886,the average correlation coefficient(R)is 0.942,and the overall pass rate is 83.3%;the average Nash efficiency coefficient of the verification period is 0.879,and the average correlation coefficient(R)is 0.949,the overall pass rate is 85.7%.Above all,it indicates that the HEC-HMS model can be perfectly applied in the research of the LRB.(3)Spearman rank correlation analysis is carried out on the landscape pattern index and the flood characteristic value.The results show that response indicators and degrees of corresponding landscape patterns and flood characteristic values are different in landscape types.Among them,the landscape index with strong correlation with construction land is the average area weight fractal dimension,dispersion and juxtaposition index;the landscape index with strong correlation with forest land is the average area weight fractal dimension and landscape aggregation index;is the dispersal and juxtaposition index;the landscape pattern index with strong correlation with cultivated land is the patch index.(4)A flood-landscape ecological risk evaluation model was introduced based on the theory of landscape ecology,and the study area was divided into 1154 risky plots with the help of ArcGIS,and the flood-landscape ecological risk values were spatially interpolated using the IDW method.The results showed that on the time scale,the high-risk and medium-risk areas gradually increased from 1996-2019,mainly from the transformation of low-risk areas.With the enhanced awareness of human protection of ecological environment,the area of higher risk region has gradually decreased in recent years.Analyzed from the spatial scale,the high-risk area as well as the higher-risk area are mainly concentrated in the main urban area of Liuyang City,Kaifu District,Furong District and Changsha County of Changsha City,while the low-risk area is mainly concentrated in the mountainous and hilly area of the watershed.(5)Based on the PLUS model,the land use change of the LRB in 2030 is simulated,and the flood ecological risk value in 2030 is analyzed in combination with the constructed flood-landscape ecological risk index.It shows that the construction land in the LRB will grow rapidly in 2030 as well.With the overall increase of the flood-landscape ecological risk value in the LRB,the low risk areas and relatively low risk areas will gradually change to medium or high risk areas. |
