城镇化平原河网区下垫面特征变化及洪涝影响研究

城镇化是人类改变地表最深刻、最剧烈的过程之一,针对平原区城镇化引起的洪涝加剧问题,以浙东沿海奉化江流域中下游平原为例,利用高分辨率遥感影像和地形图资料获取1990~2010年间下垫面特征信息,从土地利用类型、河网水系和地面高程3个方面,分析城镇化过程中平原河网地区下垫面特征变化及其对区域洪涝调蓄能力的影响。研究结果表明:平原区城镇化对下垫面的影响不仅表现为城镇不透水面的增加,径流系数的增大,同时城镇扩张过程中农田和水系转化为城镇用地,而后者具有相对较高的防洪标准,使得新建城区地面高程明显增大,河网调蓄能力亦呈不断减少趋势。洪涝模拟显示以上下垫面变化导致区域可调蓄洪涝的空间逐渐减少,洪涝风险程度加大,并呈现向相对低洼地带转移的趋势特征。

CHANGES OF UNDERLYING SURFACE AND THEIR INFLUENCES ON STORAGE CAPACITY AND FLOOD IN THE PLAIN RIVER NETWORK AREA

Urbanization is one of the most intensive processes of human activities which have changed the earth's surface, and is also one of the most important influencing factors of hydrologic process, especially for flood. Base on the high resolution image and topographic map, the paper chose the middle and lower reaches of the Fenghua River Plain as the case area, the spatial and temporal change in land use change and the river system and topography characteristics were analyzed. The result showed that the proportion of urban area increased from 13.2% to 34.1% during 1990-2010, which was mainly gained from paddy fields. The increase of impervious surface tend to lend more surface runoff, and also increase the urban ground elevation changes and decrease the drainage density and water surface rates. The submerge model shows that the decreasing in water storage would cause higher stage giving the same submergence volume, which would cause higher risk in the low-lying land in the south of the study area.