In this study, we propose a new dynamic line rate assignment strategy that responds to load intensity fluctuations of daily traffic in wavelength-division-multiplexed (WDM) mixed-line-rate (MLR) optical networks. We present Survivable Routing with Rate and Wavelength Assignment (SRRWA) and we propose an efficient shared backup path protection solution for dynamic traffic model. We prepared simulation scenarios to demonstrate the effect of handling load intensity periods over routing performance in terms of communication cost and resource utilization. We compared the results of the proposed strategy with static line rate assignment methods. The simulation results show that proposed strategy has an average performance while highest resource utilization and lowest cost values are obtained by the static rate matching line rate assignment method.