Abstract： Assessment of naturalness of stream ecosystem is an important proportion of near natural stream control.Naturalness of stream ecosystem refers to the state of a stream with no human disturbance to the process of material cycling and energy flowing in a stream ecosystem.Assessment of naturalness of stream ecosystem is to determine the deterioration degree of the ecosystem and deliver early warning or provide information for the decision-making process to maintain sustainability of streams.Here taking the Nansha River as a(research) object a theoretical framework is established to design an indexes system,including the subsets of ecological indexes,landform indexes and hydrologic indexes.A diagram of naturalness assessment is designed.In detail,among the three subsets,the ecological indexes include riparian vegetation,species diversity,individual scale of plant,biomass,width and entertainment;the landform indexes consist of plane features,diversity of transects,permeability of riverbed,erosion and deposition of river course and habitat diversity;the hydrology indexes are based on the volume variation of flow from natural state,depth and turbidity.According to the theories and methods of multi-objective linear weighting function,the comprehensive indexes of natural condition of stream is established,that is,naturalness degree.By analyzing these indexes,the naturalness condition of Nansha River is assessed,that is the naturalness condition of Nansha River was poor.Therefore,more(attention) should be paid to the disturbed streams,and further study is necessary to be carried out in this field.
2006, Vol. 4 
