River deltas form when sediment-laden rivers reach a standing body of water. Flow decelerates, sediment deposits, and channels bifurcate around depositional lobes. The network topology is governed by the competition between inertia (favoring straight channels), friction (causing deposition), and random avulsion (sudden channel switching). The result is a fractal network with channel width scaling with discharge as W ∝ Q^0.5 (Leopold-Maddock relation). Real deltas like the Nile (bird-foot) vs Niger (arcuate) differ in wave/tide vs river dominance.