The purpose of this study is to investigate the effects of the natural river conservation work and to find remedies for them, targeting Jangsu-cheon with high frequency of use by citizens among the rivers in Incheon Metroplitan City, Korea; for this, this study conducted investigations and analyses of Jangsu-cheon completed in December, 2008. As a result of investigating 3 spots for the water system of Jangsu-cheon over a total of 3 years (2009, 2010, 2014), it was found that benthic macro-invertebrates of a total of 3 phyla, 5 classes, 11 orders, 26 families, 56 species, and 980 specimens were distributed there. When they were analyzed by year, 18 families and 30 species in 2009, right after the natural river conservation work, and 22 families and 37 species in 2010, 2 years after the work, were found, with 7 species increasing in number; after that, as a result of the investigation in 2014, 22 families and 38 species were found, which tells the river has entered the stabilization stage since the recovery in 2010.Therefore, this study could identify: the water environment of the river was improved due to the natural river conservation work for Jangsu-cheon; in addition, Jangsu-cheon showed good ecological environment due to the continuous maintenance of the good wetlands in Incheon Grand Park in the upper area of the river; and the natural river conservation work of Jangsu-cheon created positive effects.

The subject of this study is the Gongchon-cheon which is one of the largest streams in Incheon and is closely related to lives of citizen. Comparative analysis is made on the changes of the environment and the ecological condition of Gongchon-cheon after the stream naturalization construction which is completed in It demonstrates the stream naturalization construction providing enough environments (dikes and rapids) for the benthic macro invertebrates. The result of the present study is similar with the river's biology index, ESB index, and KSI index, and also it is similar with the pattern of the appearance, which illustrates that the species decreased during the naturalization construction, and increased after the stabilization since the finish of the naturalization construction, and it has been confirmed that the naturalization construction provides the better environment for the inhabitation of organisms.