Hydrology l.jpg
This presentation is the property of its rightful owner.
Sponsored Links
1 / 32

Hydrology PowerPoint PPT Presentation


  • 366 Views
  • Uploaded on
  • Presentation posted in: General

Hydrology. The flow or movement of water. Hydrologic cycle. Surface Runoff. Surface hydrology focuses primarily on streams and their channels. Measuring Flow. Discharge or gage height commonly used for surface water flows Discharge or flow are measured in ft 3 /sec or m 3 /sec

Download Presentation

Hydrology

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Hydrology l.jpg

Hydrology

The flow or movement of water


Hydrologic cycle l.jpg

Hydrologic cycle


Surface runoff l.jpg

Surface Runoff

  • Surface hydrology focuses primarily on streams and their channels


Measuring flow l.jpg

Measuring Flow

  • Discharge or gage height commonly used for surface water flows

  • Discharge or flow are measured in ft3/sec or m3/sec

    • Width x depth x velocity = flow

  • Width to depth ratio


Hydrographs l.jpg

Hydrographs

  • Graph of a stream’s discharge over time

  • “Real-time” and historical data may be available through Water Resources Dept, your local watermaster or USGS

    • http://waterdata.usgs.gov/nwis

  • Water Year = Oct - Sept


Annual hydrograph l.jpg

Annual Hydrograph

10/7/01 is when flow begins to increase above 10 cfs


Peak flows l.jpg

Peak Flows

  • Watermaster has determined 1,873 cfs to be “flood stage” for this site

  • Gales Creek exceeded this level 4 times in water year 2001

  • Highest discharge for year = 4,622 csf on 1/8/02


Multi year hydrograph l.jpg

Jan-02

Multi-year Hydrograph

Flood Stage


Flood frequency l.jpg

Flood Frequency

  • Gales Creek appears to reach “flood stage” at least once per year (except 2001)

  • 1999 appears to have highest discharge for the 8 years we have data for – even higher than 1996

  • What makes a 100-year flood?


Flood frequency10 l.jpg

Flood Frequency

  • Find maximum annual discharges

    • Can query “Peak Streamflow” on USGS site

  • Rank peak discharges from largest to smallest

  • Calculate recurrence interval (RI)

    RI = # years + 1

    flood rank


Gales creek peak streamflow l.jpg

Gales Creek Peak Streamflow


Recurrence interval l.jpg

Recurrence Interval

  • Recurrence Interval

    = # years + 1

    flood rank

    = 7 + 1 = 4

    2

    For Gales Creek, 1996 was a “4-year flood”


100 year flood l.jpg

100-Year Flood

  • Requires 99 years of data

  • Only the largest flood during that 100 year period would be a “100-year flood”

  • Very few sites with 100 years of data

  • The Flood of 1996 was far from a 100-year event


Slide14 l.jpg

1996

1862 is the Historic Peak for this site


Flood recurrence at albany l.jpg

Flood Recurrence at Albany

= 117 + 1 = 3.5

34

For the Willamette in Albany, 1996 was a “3-4 year flood”


Flood recurrence at portland l.jpg

Flood Recurrence at Portland

= 29 + 1 = 30

1

For the Willamette in Portland, 1996 was a “30-year flood”


Stream channel l.jpg

Stream Channel

  • The energy from gradient can alter the

    • Sinuosity

    • Entrenchment

    • Width to Depth Ratio

      of a stream channel below bankfull


Determining bankfull channel l.jpg

Determining “Bankfull” channel

  • Top of point bar

  • Change in vegetation

  • Topographic break in slope

  • Staining or change in substrate material or size

  • Change in nature or amount of debris deposits


Entrenchment l.jpg

Entrenchment

  • Vertical containment

  • Estimated as:

    Width of stream at 2x bankfull depth

    Width at bankfull

Width @ 2x Bankfull Depth

(Floodprone Width)

Width @ Bankfull


Entrenchment23 l.jpg

Entrenchment

Entrenchment of 1.0 means the floodprone width = bankfull width


Width to depth ratio l.jpg

Width to Depth Ratio

  • Width / Depth at Bankfull


Width to depth l.jpg

Width to Depth

As the width to depth ratio increases, the stream gets wider and shallower.


Sinuosity l.jpg

Sinuosity

  • Is stream straight or does it meander?

  • How much longer would channel be if it were stretched into a straight line?

  • Estimated as:

    Channel length

    Straight length


Sinuosity28 l.jpg

Sinuosity

Sinuosity of 1.0 means the stream channel has the same gradient as the valley


Gradient l.jpg

Gradient

  • Channel slope (Rise over Run)

  • Can be difficult to measure, estimate by characteristics:


Rosgen stream classification l.jpg

Rosgen Stream Classification


  • Login