River generation pathways (fact sheet 14)

Question 1

Another name for water pathways

Answer 1

flow paths

Question 2

Two flow paths that don’t include subsurface flow

Answer 2

1. direct in-channel precipitation

2. infiltration-excess overland flow

Question 3

Direct in-channel precipitation

Answer 3

preciptation falling directly into river channels

Question 4

Another name of infiltration-excess overland flow

Answer 4

Hortonian overland flow (HOF)

Question 5

Hortonian overland flow/ infiltration-excess overland flow

Answer 5

Generated by rainfall intensities greater than the infiltration capacity of the soil

Question 6

The infiltration capacity is considered to be the permeability of the soil …

Answer 6

close to the ground surface

Question 7

Reasons why HOF isn’t significant

Answer 7

1. soil infiltration capacities are normally seen to be greater than measured rainfall intensities
2. There are less conerservative ions dissolved in river water than in rain water which suggests than rainfall is stored before discharge into the river
3. extensive overland flow is rarely observed in catchments

Question 8

Subsurface stormflow

Answer 8

The shallow underground water-pathway that delivers a rainfall response to a river response

Question 9

Evidence for subsurface response

Answer 9

the observation that the rise and fall of a river is matched by a similar rise and fall of a nearby water-table

Question 10

Three explanations for how subsurface water rapidly moves to the river-side soils

Answer 10

1. shallow water paths
2. natural soil pipes
3. wave propagation

Question 11

Shallow water paths

Answer 11

water movement in the top soil

Question 12

Natural soil pipes

Answer 12

tunnels in the soil 1cm to 1m in diameter, formed by waterflow

Question 13

Wave propagation

Answer 13

the input of storm rainfall onto a catchment generates a ‘shock wave’ in the water table that moves much faster than the water movement itself