1.2 discharge relationships within drainage basins

Question 1

size and shape

Answer 1

• smaller: respond quicker: peak flow is soon after peak rainfall
• longer: lower course respond later than upper
• circular: responds quicker than linear

Question 2

drainage density

Answer 2

• network of sewers: responds quicker
• low density: higher time lag

Question 3

porosity and permeability

Answer 3

• impermeable: overland flow: higher peak flow
• permeable: infiltration, percolation, lower peak and higher time lag

Question 4

slopes

Answer 4

• steeper: overland flow, lower time lag, higher peak flow

Question 5

vegetation type

Answer 5

• forests intercept more rainfall: less overland flow,lower peak flow, higher time lag
• winter: deciduous lose leaves: less interception

Question 6

land use

Answer 6

• more impermeable surfaces: less infiltration, more overland flow
• more basins and sewers: reduced time lag, higher peak as water return quicker

Question 7

storm hydrograph

Answer 7

shows response of river to a specific rainfall event

Question 8

what is on a hydrograph?

Answer 8

• rainfall, mm, bar graph
• discharge (m3/s) as line graph, + baseflow, overland, through flow
• rising limb : increasing flood water in river
• falling limb
• peak flow: max amount of water during event
• basin lag time: time difference between peak rainfall and peak flow

Question 9

precipitation type and intensity

Answer 9

• intense: more overland flow: steep rising limb: higher peak flow
• low intensity: infiltration:percolation: increased lag time, lower peak flow
• type: sow melt:rapid: overland flow

Question 10

temperature, evaporation, transpiration

Answer 10

• high T : warm air can hold more water : higher peak, more evaporation
• more veg cover: more interception, returned transpiration : less water reaches channels: lower peak

Question 11

antecedent moisture

Answer 11

• previous raining: saturated : overland flow : lower time lag, higher peak