Step 1: Understand splash erosion.
Splash erosion, the initial phase of water erosion, occurs when raindrops strike the soil. The impact energy of falling raindrops dislodges soil particles, making them susceptible to transport by runoff.
Step 2: Evaluate characteristic importance.
- A. Raindrop size: A raindrop's size dictates its mass (\(m\)). Larger drops possess greater mass and consequently, a higher erosive potential.
- B. Terminal velocity: This is the stable speed a freely falling drop achieves when air resistance balances gravity. Increased terminal velocity (\(v\)) results in a more forceful impact.
- C. Kinetic energy: The impact energy of a raindrop is calculated as \(KE = \frac{1{2}}mv^2\). This value directly quantifies the raindrop's capacity to detach soil particles, being dependent on both mass and terminal velocity.
- D. Drop size distribution: Rainfall comprises drops of varied sizes. The cumulative erosive impact of a storm is determined by the distribution of these sizes. A storm with a larger proportion of big drops will exhibit greater erosivity than one with equivalent total rainfall but composed of smaller drops.
Step 3: Conclude the correct combination.
All four factors—size, terminal velocity, resulting kinetic energy, and the distribution of drop sizes—are critical in determining rainfall's erosive power.