Transcript Interactions class 1. Getting and understanding watershed flux data 2. Influence of Large Woody Debris (LWD) on rivers 3.

Interactions class
1. Getting and understanding
watershed flux data
2. Influence of Large Woody Debris
(LWD) on rivers
3. Influence of Hillslope materials and
processes on rivers
4. Influence of the Atmosphere on
rivers, 1927 flood example
1
Sediment Transport Through Rivers
Bedload -- material moving along the bed,
shear forces exerted by water sufficient to
move clasts -- rarely measured (at % level)
Suspended Load -- material kept in the water
column by turbulence and lift forces (easy to
measure in grab samples)
Dissolved Load -- material in solution
(easy to measure in grab samples)
Bedload usually <<< than suspended load and ignored
Dissolved load varies, usually < than suspended load
Sampling for suspended load…….
1
1
Mass Loadings and Erosion
Rate Estimation
Integrate suspended load over all flows (mass/time)
+
Integrate bedload load over all flows (mass/time)
+
Integrate dissolved load over all flows (mass/time)
Calcium, Rio Puerco
Dissolved 1
load varies
over time
and
discharge
700
500
400
300
200
100
0
10/4/58
3/26/64
9/16/69
3/9/75
8/29/80
Date
2/19/86
8/12/91
2/1/97
Rio Puerco 1960-1990
10000
Discharge (cfs)
Ca (ppm or mg/kg)
600
8000
6000
4000
2000
y = -0.2709x + 1707.5
R2 = 0.012
0
0
500
1000
1500
2000
Dissolved Load (mg/kg)
2500
3000
1
USGS Water Quality Data on line
Dissolved and Suspended Load
http://nwis.waterdata.usgs.gov/nwis/qwdata?site_n
o=04282815&agency_cd=USGS&begin_date=&e
nd_date=&format=html_table&inventory_output=
0&rdb_inventory_output=file&date_format=YYY
Y-MMDD&rdb_compression=file&qw_sample_wide=0
&submitted_form=brief_list
1
Data Manipulation
1.
2.
3.
4.
Data supplied in mg/l (1/1000 g per 1000 g) or ppm
Need to sum all constituents (Ca, Na, Mg, Cl, C03)
Need to know daily flow (in liters). How many liters/m3?
Multiply concentration by flow

Ca
15 mg/l 8 mg/l
Na
Mg
Flow
3 mg/l
4 mg/l 0.1 m3/s
m3 = 100 cm* 100 cm* 100 cm = 106 cm3 =103 liters
100 l/s* 60s/min*60min/hr*24hr/day*15mg/l*0.000001kg/mg=
129.6 kg/day dissolved load
1
TO GET YEARLY LOAD
Integration over all flows is a non
trivial problem!
Need Rating Curves (suspended, dissolved, bedload)
Suspended Load
Note Scatter
Hysteresis loop
Other Approaches…Reservoir
trapping (may miss dissolved)
Nahal Yael, Negev Desert
1
1
SEDIMENT YIELD
= what comes out
= or ≠
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Timescale
Steady state
Human impact
Episodic disturbance
SEDIMENT GENERATION
= Material generated
by erosion
1
Trimblegram
Importance of Vegetation
Bank Stabilization, effective soil cohesion
Source, Large Woody Debris
2
Queets River,
Olympic Penninusla,
Washington
Large Woody Debris
2
2
Queets -Meander Jam
2
Most rivers 2
have been
de-snagged
Montgomery et al., 2003
Putget Lowland
2
Reach Scale Effects
2
In-Channel Effects
2
Valley Bottom Effects - Wood
adds Complexity
Nisqually River w/wood
2
Effects Felt
Downstream
2
2
• Briaded Rivers
– Weak banks
– High sediment load
– Flashy
QuickTime™ and a
TIFF (Uncompressed) decomp
are needed to see this pictu
2
Influence of Hillslope Materials and
Processes on Channels
Slides are frequent
in mountain
environments
Example: Chris Brummer, Squire Creek, North Cascades, Slide into Channel
3
3
Toe of Slide - QT VR
3
Sediment and Woody Debris
Supply - pulsed delivery
3
Stepping of Channel Profile
Damming of ephemeral lakes by slides
Outlet,
overtopping dam
Help set channel roughness
boulders may be delivered by
older slides….or underlying
bedrock or till
3
Here, stratigraphic evidence this 3
is not the first slide…
Recent Slide Debris
Older Slide Debris
1927 Flood
• Antecedence --Rainfall
during the month of
October averaged about
150 percent of normal
across the state. In
northern and central
sections, some stations
received 200-300 percent
of normal.
4
Major Channel Change and
Realignment - Proctor
4
Major damage at
constrictions, e.g., bridges
• Isohyet map
4
4
Winooski-Burlington response
Cause of the
1927 Flood
Mositure-laden air was forced
to rise as it encountered
the Green Mountains,
resulting in torrential
downpours. Rainfall in
Northfield totaled 1.65
inches from 4:00 am to
11:00 am on the 3rd, with
4.24 inches falling from
11:00 am to 8:00 pm. The
total from late evening of
the 2nd to late morning on
the 4th was 8.71 inches.
4
Wednesday Lab
•
•
•
•
Meet in classroom
Move to the field, Bolton
Cooler weather, be prepared.
Wear sturdy shoes please