Week 8 - Week 8, Geo 103 Outline: How do we measure stream...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Week 8, Geo 103 22/10/2007 14:00:00 Outline: How do we measure stream flows? Storm Hydrographs Seasonal hydrographs Floods Factors influencing flow hydrographs: Climatic Factors Precipitation type (snow/rain) Rain intensity and duration Storm size and direction Geological factors and surface cover Rock and soil types Frozen ground Vegetation Other Factors: Land use – urbanization, logging
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Lakes Water diversion, river management Physical characteristics of drainage basion: Topography Drainage system density Surface gradient Watershed: entire land area or basin above a specific point on a stream  where water flows across the surface into a stream. Figure 14.13 Floods and Flood Analysis Flooding occurs when the stream discharge cannot be contained within the  channel and part of the discharge overflows onto the floodplain. Probably cause the greatest loss of life and property damage of all natural  hazards. In rivers, they mainly occur in response to  o Rainfall events o Snowmelt events The largest floods in Coastal BC come from combination of rain and  snowmelt. (rain-on-snow events). Floodplain:  build up by the river during lateral migration and by deposition of fine  sediment (clay, silt, and fine sand) during flooding.
Background image of page 2
Why care about Floods? In the decade 1986-1995 alone: 34% of all natural disasters worldwide were floods 31% of all economic losses from natural disasters were from floods. Flood Frequency Analysis Large floods are more dangerous and more damaging than smaller floods. In  order to estimate the probability of a floods of a given size, we use flood frequency  analysis. P =R / (n+1) P = probability that a flood of a given size will occur this year R = rank of each peak annual flood measured, by discharge n = number of years data has been collected. Recurrence interval (return period)  = the average interval of time between floods of the  same magnitude (size) = the inverse of the probability i.e. (n+1)/R Example: Fraser River at Hope
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The Fraser river flood levels have been measured since 1950. In 1972, the gauge on Fraser River at Hope recorded a flow of 13000 m3/s on  June 16 th . That is the flood of record for 1972, and the highest on record since  1950   i.e. R=1 In 2004, the flood of record was 6760 m3/s and occurred on June 10 th . This  flood was only higher than two other flood events since 1950. i.e. R=54 Fluvial Processes and Landforms – CHAPTER 14 Why study rivers? Natural Hazards (floods)
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 15

Week 8 - Week 8, Geo 103 Outline: How do we measure stream...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online