Riverine wetlands were reduced and damaged by dredging of rivers and constructing parks in wetlands by Four
Rivers Project from 2008 to 2013. Therefore, replacement wetlands were constructed for the compensation of
wetland loss by the government. However, It is not enough to manage replacement wetlands. In order to manage
the wetlands efficiently, it is necessaty to assess the functions of the wetlands and to manage them according to
their functions. Here we performed functional assessments for a replacement wetland called Gangcheon wetland
using the modified HGM approach. Hydrological, biogeochemical, animal habitat, and plant habitat functions for
the wetland were assessed. To assess the functions, we collected informations for modified HGM approach from
the monitored hydrologic data, field survey, published reports and documents for before and after the project,
and hydraulic & hydrologic modeling. As the results of the assessment, the hydrological function for the
replacement wetland showed 65.5% of the reference wetland, biogeochemical function showed 66.6%, plant
habitat function showed 75%, and animal habitat function showed 108.3%. Overall, Gangcheon wetland function
after the project was reduced to 78.9% of the function before the project. The decrease in hydrological function
is due to the decrease of subsurface storage of water. And the decrease in biogeochemical & pland habitat
functions is due to the removal of sandbank around the Gangcheon wetland. To compensate for the reduced
function, it is necessary to expand the wetland area and to plant the various vegetation. The modified HGM used in this study can take into account the degree of improvement for replacement wetlands, so it can be used
to efficiently manage the replacement wetlands. Also when the wetland is newly constructed, it will be very
useful to assess the change of function of the wetland over time.