Which water route commonly gives a river a rapid response to a storm?

• Groundwater travelling through deep rock and sediment
• Throughflow travelling through water-filled soil spaces
• Surface runoff moving towards a channel

Surface runoff enters a tributary within a drainage basin. Which river system does that tributary feed?

• The river system draining that basin
• A river system across the surface divide
• Every river system in the surrounding region

A drainage divide separates the surface drainage of neighbouring river basins.

During gentle rain, most water infiltrates and little runs over the surface. The river rises slowly. Which explanation is best supported?

• Gentle rain sets the response speed regardless of the water's route
• Water reaches the river by slower soil and groundwater routes
• A slow rise proves that a large lake stores rainfall within the basin

After a storm, river discharge rises rapidly and peaks soon after peak rainfall. What does this show?

• A slow response that cannot cause any flooding
• A rapid response with a short rainfall-to-flow lag
• A long delay identifying groundwater as the only route

Covering soil with impermeable concrete increases infiltration into that soil.

In both basins, peak rain occurs at noon. Peak discharge is at 1 pm in A and 6 pm in B. What comparison is supported?

• A has a longer lag and must contain more groundwater
• A has a shorter lag and reaches peak discharge sooner
• B has less flood risk solely because its discharge peaks later

An estate adds impermeable paving and drains storm water directly to a river, without storage. Why might flood risk increase downstream?

• Reduced infiltration sends runoff quickly to the river
• The drains store storm water until groundwater levels fall again
• Paving increases infiltration and delays the river's storm response