The construction of irrigation and water conservancy was initiated on the North China Plain in the 1950s, which played a significant role in the saline-alkali soil improvement and flood discharge. However, the phenomenon of filling agricultural drainage ditches has become common in the North China Plain since the 1990s. It is necessary to know the condition of filling agricultural drainage ditches and flood disasters related with this phenomenon. Nowadays, there are few researches to analyze the condition of filling agricultural drainage ditches. In order to enrich existing studies, this research took Cangxian County which was battered by flooding and soil salinization in lower plain area as a case study, and explored the condition of filling agricultural drainage ditch and the flood disaster. The changes of drainage ditch area and spatial variation were analyzed based on land use databases of Cangxian County in 1992 and 2010 using the method of GIS (geographic information system). Then, the condition of filling agricultural drainage ditch was investigated by means of the field research in Nan Gutun Village. This village was one of the most densely populated agriculture villages in Cangxian County. Interviewing with the village committee members and the villagers over 70 years old, we learned about the local agricultural production mode, the way of life, the changes of agricultural drainage ditch and its mechanisms from 1960s to now. Finally, we analyzed the risk of flood disasters from the aspects of precipitation trends, percentage of precipitation anomalies, underground water level, drought/flood frequency, relationship between soil water capacity and rainfall, and upland water condition. The results showed that from 1992 to 2010, the area of drainage ditches in Cangxian County reduced by 37.73%. Meanwhile, the proportion of drainage ditches in Cangxian County decreased by 2.03% and the farm ditches was the most serious in being filled. The results of flood disaster analysis showed that the annual precipitation had an obvious downtrend and the seasonal precipitation was evenly distributed. With the underground water level lowering at the average speed of 1-2 m/a, soil water supplement through soil capillarity was decreasing. This made the storage capacity of soil water enlarged before rainy season. Based on soil physics, 1 m water-free soil could contain approximately 140 mm precipitation, which played a significant role in slowing down the surface runoff. At the same time, the actual water flow in the upstream was decreasing. Moreover, China’s rapid urbanization and industrialization is accompanied by a continuous growth of water use, and upland water is mainly used for cities, which results in the decrease of upland water. In consideration of all condition, the risk of flood disasters was reducing according to the precipitation, soil water capacity and upland water. In other words, under the constant climate circumstances, the condition of filling agricultural drainage ditches did not increase the risk of flood in the majority of years. But we found in the field research that the risk of flooding increased after the heavy rain. Based on the results above, we suggest that the government should take terrain, underground water level and soil into consideration in the redesigning of drainage ditch systems, and attain the goal of maintaining high and stable yield of grain, farmland infrastructure protection and requisition-compensation balance of cultivated land through the scientific planning of water conservancy construction and land consolidation.%近20 a来，华北平原普遍出现平填农田排水沟现象。为分析排水沟平填状况及平填后洪涝灾害的发生风险，该研究基于土地利用调查数据库，以地处华北低平原的河北沧县为例，运用ArcGIS10.2分析1992－2010年间沧县排水沟面积变化情况，采用实地调查法来验证和分析排水沟平填现象，并从降水量、地下水位、土壤水、上游来水等方面对排水沟平填后可能发生的洪涝灾害风险进行分析。研究结果表明：1992－2010年间，排水沟面积减少了37.73%，其中农田末级排水沟平填最为严重，排水体系贯通性下降；通过水文要素分析得出沧县地区洪涝灾害的发生风险有所降低，平填末级排水沟对洪涝灾害的发生影响不大。基于此，该文认为华北平原的不同区域，应根据所处地形地势、地下水位、土壤状况来重新设计排水体系，通过土地整治，使其既能增加耕地面积，又不致引发洪涝灾害。该研究结果可为土地整治规划及农田基础设施建设提供参考。
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