1. Notebook Collection Collecting hard copies now OR
Electronic versions using Catalyst drop box
Due by 5:30 pm today
Use website for link
If you are not able to turn in your notebook see me or Dan ASAP

2. Urban Soils & Seattle Examples
ESRM 311 / SEFS 507
Week 4

3. Urban Soils Outline What are urban soils? Hazards
How they differ from unmodified soils
Physical properties
Hydrologic cycle
Hazards
Denny re-grade
Earthquake hazards
Example of Urban Soil
Magnuson Park
Soil Pits

4. How would you define an Urban Soil?

5. Urban Soil
Bockheim (1974) gives an appropriate and useful definition of urban soil:
“A soil material having a non-agricultural, man-made surface layer more than 50 cm thick, that has been produced by mixing, filling, or by contamination of land surfaces in urban and suburban areas”

6. Soil Physical Properties
Horizons
Structure
Texture
Color
Moisture
Temperature
Single
Grained
Granular
Blocky
Prismatic
Columnar
Platy

7. Idealized Soil Profile
Layered characteristics
Example forest
Litter layer
A horizon
Organisms or gravity
Plant root growth
E horizon
Organic acids through leaching
B horizon
Clays accumulate
C horizon
Parent material

8. Urban Soil Characteristics Urban Soil
Great vertical and spatial variability
Modified soil structure: compaction
Waste materials and other contaminants
Restricted aeration and water drainage
Interrupted nutrient cycling and modified soil organism activity
Surface crust; usually hydrophobic
Modified temperature
High pH

9. Soil Mixing Slope that was back filled Original profile covered
Organic layers covered (13)
Fill materials used
Refuse, Clayey fill
Would you build a house on the fill?
Cold weather
Organic matter

10. Structure and Compaction
Disturbed, displaced or compacted
Reduce pore space and increase bulk density
Low organic matter
Soil organisms activity less
Low frequency wet-dry or freeze-thaw
Less aggregation and structure formation
Compressive forces
Vehicle, water, human or paving
Reduced vegetative cover
Bare soil, erosion, crust formation

11. Crusting and pH Crusting
Precipitation on bare or exposed soil sorts the finer matter and fills small pores
Impervious surface
Barrier for plant growth pH
Ca increase soil pH
Sources:
De-icing compounds
Weathering building rubble
Calcium-rich water in gardens

12. Water movement and Aeration
Urban environment limits aeration and infiltration
Water movement restriction
Mixing of layers
Impervious surface

13. Hydrologic Cycle in Urban Areas
Relationship between impervious cover and surface runoff. Impervious cover in a watershed results in increased surface runoff. As little as 10 percent impervious cover in a watershed can result in stream degradation.
40% evapotranspiration
30% evapotranspiration
55% runoff
10% runoff
10% shallow infiltration
25% shallow infiltration
25% deep infiltration
5% deep infiltration
75-100% Impervious Cover
Natural Ground Cover

14. Decomposition Water movement is restricted Little aeration
Limited root zone
Less favorable for organisms

15. Denny Re-grade
Removal of Denny Hill

16. Denny Re-grade

17. Hazards Earthquake hazards Liquefaction:
Water-saturated sandy soils that lose strength during earth shaking

18. Hazards Earthquake hazards Site Class
National Earthquake Hazards Reduction Program (NEHRP), site class where soils amplify ground shaking

19. Urban environment affects soil?
Covering of soil
Disturbed water cycle
Nutrient and decomposition limited
Horizon mixing

20. Example Urban Soil Magnuson Park
1855: surveyed alder grove, Douglas fir forest with trees 2-6 feet, Cedar, streams and wetlands
Mid 1930’s: conversion to military base, trucked in hundreds of loads of fill, Mud lake, the marsh and Pontiac Bay covered
Current Day: restoration of the park

21. Magnuson Park
Site Characteristics
1953
1927
2011

22. Soil Pits Dug three soil pits Forested Area Cottonwoods Grassland
Characteristics
Horizons
Bulk density pH
Structure

23. Sites and Pits
Site 1
Site 2
Site 3

24. Horizon Depth (inches)
Survey Results
Site
Horizon Type
Horizon Depth (inches)
Texture
Moisture Content pH
Structure 1 A
Clay Loam
29.7%
5.41
Crumb Structure (small rock or shot Fe)
Bts
25.5 – 14
Sandy Clay
21.2%
5.00
Clay Crumb
Bts2
14 – 6
82.1%
4.75
Saturated Clay (plastic limit) 2
28 – 25
Silt Clay
46.0%
5.32
Organic with rocks B1
25 – 17
Sandy Loam
25.2%
5.45
Fill with Fingering B2
17 – 12
26.6%
5.80
Clay with Moddles B3
12 – 0
Loamy Sand
28.0%
6.07
Sand with Organic Matter 3
23 – 17
31.0%
5.37
Crumb Structure
17-0
27.9%
5.95
Blocky
Bulk Density
Horizon
Moisture
Content
Volume (cm3)
Bulk Density (g/cm3)
26.5%
177.11
1.39
13.1%
68.70
2.45
16.2%
2.10

25. Magnuson Park Vegetation indictor of underlying soils
Horizon development
Natural horizon, moved? (site 1)
Water logged (site 2)
Hill area (site 3)
Poor drainage, site 2 water table 2 feet
High bulk density
Trees dying off around site 2

26. Urban Soils Urban soils vs. idealized profile Characteristics
Variable horizons
Modified soil structure
Compaction
Waste materials mixed in
Interrupted nutrient cycling
Low soil organism activity
High pH
Local examples
Denny Hill re-grade
Magnuson Park