Unit 6: River systems

Question 1

when will surface runoff occur

Answer 1

• areas where more than half of the annual runoff id derived from snowmelt
• surface runoff =overland flow (only occurs with excess water)
• other causes are precipitation, and glacier melt
• runoff occurs only when infiltration rate is too slow and when depression storage is full
• ground water NOT necessarily saturated

Question 2

what were the differences in the drainage system of north ameria in pre glacial period compared to present

Answer 2

• pre: drained mainly to north east and the hudson bay and very little to the mississippi
• post: very little hudson bay drainage, mackenzie and mississippi and st lawrence drainage. more dendritic in the south and less in the north and more significant lakes

Question 3

dendritic patters are typical of what kind of environemnt

Answer 3

• flay lying or relatively homogenous rocks and impervious soils. slow velocity and less drainage

Question 4

deranged drainage patterns are typical of what kind of environment

Answer 4

• resulting from a high water table and a flat or gently undulating topographic surface
• normally these conditions are met in areas of glacial till plains

Question 5

describe the characteristics of meandering, straight and braided channels

Answer 5

• meandering: sinuosity is high, faster current on the outside of the bend and deposits sediment on the inside bed
• straight: incline of more than 10%, fast flow, makes deep channels
• braided: glacial outwash is typical, low slope and slow current and low volume

Question 6

what effect do beavers have on the local hydrology of canadian rivers

Answer 6

• one of the primary means of lake and wetland formation
• moderate flooding, stabilize water supply
• recharge groundwater
• improve water quality
• reduce erosion
• develop new wetlands
• increase biodiversity
• improve fertility

Question 7

choose a river discussed in lesson nine and describe its characteristics

Answer 7

• st lawrence river
• it waas made after the galcier and major fluvial system for ontario

Question 8

what is a storm hydrograph

Answer 8

• a ploy of streamflow vs time for a single storm event

Question 9

how does antecedent rainfall affect the form of a storm hydrograph

Answer 9

• infiltration rate governed by antecedent rainfall
• previous rain = ground already soaked = rapid water rise