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The river floodplain system is the basis of material and energy exchange between the river and floodplain in a region, and its connectivity is an important basis for water health evaluation and ecological protection. To clarify the effects of hydrological connectivity changes on vegetation, the graph theory method was improved based on ArcGIS and a quantitative evaluation model of river floodplain system hydrological connectivity was established. Taking the Jiahetan river floodplain system in the lower Yellow River basin as an example, the variation trend of hydrological connectivity in this region in the last 36 years and the influence of the Xiaolangdi Dam on hydrological connectivity was analyzed, and the response law of vegetation in the floodplain to the change of hydrological connectivity under different water surface ratios was obtained. The results show that because of Xiaolangdi Dam operation, the hydrological connectivity and vegetation coverage of Jiahetan increased by 28.09 % and 17.73 % on average, respectively, in the flood season. In the non-flood season, hydrological connectivity decreased by 22.91 % and vegetation coverage increased by 164.82 % on average. It is beneficial for vegetation growth to keep the hydrological connectivity value around 0.4 in the flood season and 0.3 in the non-flood season. These results provide a quantitative analysis technique for the evaluation of river floodplain hydrological connectivity, with the characteristics of a simple evaluation process and good applicability, and have important scientific significance and wide application value in providing guidance and decision-making assistance for the protection and restoration of floodplain water ecology, river system connectivity planning, and water and sediment regulation.
Zhang et al. (Tue,) studied this question.