Hack's Law: The Simple Math That Governs Rivers and Their Deltas

Why Are Rivers So Mathematical?

A 2026 study in Science reveals that Hack's law, a scaling law long known to describe river networks, also applies to river deltas. This law, which states that a stream's length is proportional to its drainage area raised to the power of 0.6, reflects the most energy-efficient way for water to flow downhill. The finding extends the law's reach and deepens the mystery of why such chaotic systems obey simple mathematics.