Why does very dry climate limit river valley formation?

In very dry climates, the formation of river valleys is limited primarily by the lack of sufficient water to sustain consistent fluvial erosion. Because river valleys are typically created by the incising action of rivers, the absence of regular discharge prevents the continuous degradation of the landscape.1234

Furthermore, arid regions often lack the protective vegetative cover that stabilizes soil in more humid environments. While rare, intense rainstorms in these areas can trigger significant fluvial activity, but in hyperarid regions, rainfall is so infrequent that these processes remain largely ineffective. In such environments, the landscape is instead dominated by eolian (wind-driven) processes, which may even bury older, relict paleovalleys that were formed during wetter climatic periods. Ultimately, because valley size is generally related to river size, the limited flow in dry climates restricts the ability of rivers to carve or maintain expansive valley systems.254