We consider the cascading failure process in interdependent power-communication networks, where the power grid provides the required energy for the communication nodes, and the communication network facilitates the monitoring and controlling the power networks. The proposed system model considers the flow dynamics in both networks and the failure rollover to study the cascade process in the system and capture the possible beneficial and adverse effects of interdependency between the networks. We suggest weak and strong interdependencies models that determine how and to what extent the loss of controllability after failures impacts the power network and a congestion-aware load balancing scheme that exploits the system state to decrease the density of severe cascades. The results of the cascading failure processes on data from two power networks are provided and discussed in terms of the average unserved load in the power network and the number of failed nodes in the communication layer in different scenarios. We find that increasing the coupling is beneficial in most cases; however, considering the robustness of each network and the nature of the interdependencies between the two networks, over-coupling can decrease the system's robustness against failure cascading in certain scenarios.