Debris Flow Hazard Assessment Using Set Pair Analysis Models:Take Beichuan County as an Example

Assessment of debris flow hazards is important for developing measures to mitigate the loss of life and property and to minimize environmental damage. Two modified uncertainty models, Set Pair Analysis （SPA） and modified Set Pair Analysis （mSPA）, were suggested to assess the regional debris flow hazard. A ease study was conducted in seven towns of the Beichuan county, Sichuan Province, China, to test and compare the application of these two models in debris flow hazard assessment. The results showed that mSPA only can fit for value-variables, but not for non value-variable assessment indexes, Furthermore, as for a given assessment index xi, mSPA only considers two cases, namely, when grade value increases with xi and when grade value decreases with xi. Thus, mSPA can not be used for debris flow hazard assessment but SPA is credible for the assessment because there are no limitations when using SPA model to assess the debris flow hazard. Therefore, in this study SPA is proposed for assessing debris flow hazard.

Integrating morphological spatial pattern analysis and the minimal cumulative resistance model to optimize urban ecological networks: a case study in Shenzhen City, China

Background:With the increasing fragmentation of landscape induced by rapid urbanization,the construction of ecological networks is of great signifcance to alleviate the degradation of urban habitats and protect natural envi‑ronments.However,there is considerable uncertainty when constructing ecological networks,especially the difer‑ent approaches to selecting ecological sources.We used the southern Chinese city of Shenzhen as a study area to construct and optimize ecological networks using a coupling approach.Ecological source areas were extracted using morphological spatial pattern analysis(MSPA)and the landscape index method.Ecological networks were con‑structed using the minimal cumulative resistance(MCR)model and the gravity model.Stepping stones and ecological fault points were added in corridors to optimize the ecological network.Results:Ten core areas with maximum importance patch values were extracted by the landscape index method as ecological source areas according to MSPA,after which corridors between ecological sources were constructed based on the MCR model.The constructed ecological networks were optimized using 35 stepping stones and 17 ecologi‑cal fault points.The optimized ecological networks included 11 important corridors,34 general corridors,and seven potential corridors.The results of corridor landscape-type analysis showed that a suitable ecological corridor is 60 to 200 m wide.Conclusions:Overall,our results imply that ecological source areas can be identifed virtually,and that ecological networks can be signifcantly optimized by combining MSPA and MCR models.These results provide a methodologi‑cal reference for constructing ecological networks,and they will be useful for urban planning and biodiversity protec‑tion in Shenzhen and other similar regions around the world.