Field Work in Geography
What will writing assignments be?
Go over class schedule and grading system
1. Writing
Resume instructions (first resume due Feb 8)
2. Service Learning
3. Fieldwork
What is “Service Learning”?
Look at class web site
What is “Fieldwork”?
What are good field notes?
What is a “regional geography” course?
Possible topics in a regional course?
Our fieldwork
region
What is a
watershed?
Physical characteristics of Dog River’s watershed
Rainfall
Slope factor in erosion/deposition
Soils
Tidal stream
1
Cumulative rainfall graph H. Georges, 1998
ºF
In.
Sediment plume
from Moore Creek
into Dog River after
Hurricane Georges
Where did it all
come from?
Over time, stream develops a typical horizontal profile 
Graded stream: slope of water and channel size provide
sufficient velocity to transport the sediment load eroded
from the drainage basin.
elevation
Tributaries,
headward
erosion &
downcutting
Lateral erosion,
transport, some
deposition
Distributaries,
deposition at
base level
Stream length
2
Profile south of Airport from Schillinger to Mobile River
Terrace = remnant of
former floodplain
Soils in DRW
Sandy hills easily eroded
Heavy clays in former wetlands
mainly on terrace
against valley wall
1935
McGregor
Wragg
Swamp
Sage
Sedimentation in a tidal stream
Flocculation of clays in lower part of Dog River
clay particles negatively charged
repel each other in fresh water
salty water neutralizes charge
Airport
clay particles clump together
settle out
3
Human factors in the Dog River Watershed
Urban sprawl
population density
impervious surfaces
Polluted runoff
Sediment is #1
Point versus non-point
Unpaved roads and parking lots
Loss of wetlands and riparian buffers
Stream channelization
Natural setting, vegetation, permeable surfaces, wetlands
Loss of wetlands
1957
Note
drainage
canals in
Wragg
Swamp
4
Urban setting:
less vegetation,
impermeable
surfaces, less
wetlands,
channelized
flow
Spring Creek before
Spring Creek on Sept. 23, 2007
Spring Creek after
Why do we alter streams?
Usually to “prevent” flooding
Issues affecting Dog River’s tributaries
Low dissolved oxygen
Bigger, deeper, straighter, cleaner ditches
remove water faster
make downstream flooding worse
increase erosion
carry high sediment load
reduce groundwater recharge
Sewage
Trash
Sediment
#1 pollutant nationally
What else could we do?
Retaining ponds, wetlands, floodways
slow water down
eliminate flooding AND sediment problems
initial costs high
property acquisition
5
Terms to know
“Point” versus “non-point” pollution sources
Turbidity
Cloudiness of water
Fast moving water carries more sediment
Measured in NTU
Nephelimetric Turbidity Units
Sedimentation/Siltation
Filling in of low place with sediment/silt
University
Fecal coliform
bacteria associated with gut of warm blooded animals
Azalea
Airport
SSO: Sanitary Sewer Overflow
Sewage contains nutrients that can lead to algal
overgrowth
6
Trash floating down drainage ditch after rain.
Where does it come from? Where does it go?
http://www.youtube.com/watch?v=in9-WblXJcg
Sediment in Halls
Mill Creek comes
primarily from
development in west
Mobile
Home builder sediment runoff
Where does it go?
Sedimentation in Moore Creek
7
Silt fence, rip rap, and hay bales are physical BMPs
Preventive Measures
BMPs (Best Management Practices)
Procedural
Clearing just before construction
Minimal clearing
Natural vegetation barriers
Access road placement
Physical
Hay bales
Silt fences
Rip-rap, gabions
Erosion cloth
Sometimes they work, sometimes they don’t
Erosion cloth...when the work is all done
Gabions: rocks in wire cages
Better than concrete ditches
City versus County jurisdiction
8
Political jurisdiction
DRW 70% in city, 30% in county
Alabama
Same as Federal
Alabama Department of Environmental Management
Laws (All must be at least equal to federal standard)
ADEM responsible for enforcement
Mobile County
Federal
No activity can cause turbidity to increase more
than 50 NTU above background turbidity
Same as Alabama
City of Mobile
Cannot let runoff impact other property
No numbers specified
Today’s assignments
Writing a hypothesis
Team reconnaissance next week
No regular class
Sub-basin assignments
Get topographic maps that you NEED to cover your
assigned subbasin. Tape them together if you need
two or more.
9
Trace all assigned streams and ditches in marker, so they
are clearly visible on your topo map
Find the actual divides that separate your sub basin from
adjacent ones and mark them in pencil until I check them
(my assignment map is generalized)
Plan your route using the city map and topo map
1. What is Dog River like in your subbasin?
2. What is the general land use in your subbasin?
3. What do you see that might affect water quality, both
good and bad?
4. Generate 2 hypotheses per person, write them down,
turn them in on Feb 11.
5. Document your route and your findings with field
notes and photographs (20 per person, no repeats)
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