Most large rivers in the industrialized countries are heavily degraded due to channel-straightening and levee-construction. As a result, floodplains have been reduced and once flood-prone zone which is separated from river has been used as a cropland or residential area. Recently, floodplains are increasingly valued for their properties such as flood control, recreation, ecological habitat and so on. There are also some projects that make space for the river all around world. However, selection of restoration site only depends whether historical water-course was or not before levee-construction because a quantified procedure for prioritization to expand river area is not structured.

In this study, the simple assessment scheme has been developed to evaluate the change rate of ecological function before/after levee-construction and the feasibility of river expansion project. The evaluating scheme of ecological values are composed of linear and areal fragmentation, which explains ecological connectivity conversely in river areas. The feasibility factors are the distance from the river and the type of land-use.

This scheme was applied to past (1918, before levee-construction) and present (2007, after levee-construction) Mankyung River area in Korea. A GIS model was adopted for calculating, analyzing, and presenting site-priority using the Digital Elevation Model (DEM). Comparison results show that the evaluation grade was decreased. It is also founded that linear fragmentation due to roads and rails is greater than areal fragmentation due to difference of land-use in this study area. Finally, the site selection for river expansion is performed considering the sorted comparison results and feasibility factors.