In order to investigate the influence of environmental effects on natural frequencies, we use local distance correlation (LDC) to accommodate the nature of environmental data, that is local stationarity. LDC pattern help to identify similarities and differences of these influential variables. In addition to that, the examination of LDC pattern between frequencies of both the same and different mode types allow to compare their temporal progress. The study uses data from a monitoring system installed on the steel railway bridge KW51 in Leuven in Belgium.