Channel networks are ubiquitous in our world. They are found in biological systems as intricate blood capillary structures, in natural landscapes as river drainage patterns, and even in various human transport designs such as urban water supply networks. This thesis embarks on a comprehensive exploration of over a century of Optimal Channel Networks (OCNs) literature. Our aim is to formulate a unified model that encapsulates and generalizes the cumulative efforts in this domain. In our pursuit of this ambitious endeavor, we have provided a more robust mathematical description of the optimization process, revealing that the commonly assumed 'principle of local optimality' is, in fact, dispensable.