Critical flows of goods and services, such as energy, information, transport, and food, are imperative for society's functionality. Hence, it is important to study the vulnerability of these flows and how the disruption of one may affect another. However, holistic overview and understanding of critical flows are largely lacking. It is not trivial to co-analyze flows of heterogeneous nature: assets, spatial distribution, and underlying infrastructure differ widely. This causes difficulties in establishing a common flow concept for holistic analysis. This poster presents ongoing work regarding conceptual framing of critical flows and a three-tier modeling framework with an illustrative case in a Swedish setting. The concept of critical flows aims to shift focus from sector-specific security management towards interdependencies between sectors, societal entities, critical infrastructures, and supply chains, thus focusing on a meso-level to complement more traditional micro- and macro-levels. Here also focusing on consequences at national or regional levels. A broad interpretation of what constitutes a flow is used in this approach to accommodate and integrate a wide variety of flows within the same framework where the salient properties of critical flows and their interdependent behavior are captured to achieve a system-of-systems perspective. This research further takes a modeling and simulation (M&S) approach to operationalizing the critical flows concept. The goal is to enable a multitude of resilience-oriented analyses through simulations and to contrast and compare risks and vulnerabilities across and between different flows. Three tiers of model granularity are proposed, each with structural, functional, and interdependency models. The first tier of the model is exemplified by a Swedish case and shows the regional vulnerabilities of the road network in relation to the flows of diesel and grain. The results show significant regional differences in vulnerability, where some regions are self-sufficient and hence unaffected by road disturbances, while other parts, mainly the north, are more severely affected as dependent on imports from other regions. There are also differences among flows; diesel is more vulnerable to road disturbances than grain. The study highlights the value of a joint conceptualization and an M&S approach for analyzing interdependent critical flows upholding society.