Using High-Resolution Airphotos for Assessing Landscape Change Torre Jorgenson
It s All a Matter of Scale Landsat TM 28-m pixel
Ikonos Fused 1-m pixel
Digital Camera 0.2-m pixel
Examples of Landscape Change Inventory (1 time) vs Monitoring (repeat) Coastal Erosion Waterbody changes Floodplain Dynamics Thermokarst Vegetation Disturbance and recovery
Coastal Changes Geomorphic Change 30 25 Areal Extent (% area) 20 15 10 5 0 % overall change Dune Changes Tidal uplift changes Shoreline- Beach Changes Channel changes Overwash succession
Waterbody Changes
Nechelik Need SWAN photos SCALE IN MILES N 0 1 2 Areas of Erosion and Deposition Eroded Riverbed/Sandbar Area (%) 1.3 Channel Riverbed/Sandbar Deposition 2.6 Channel Unchanged Riverbed/Sandbar Thaw Basin Drainage/Deposition 7.6 1.8 East Other Eroded Terrain 1.0 Colville River Unchanged Terrain Lake-level Change Unchanged Water 58.8 0.9 26.1 Proposed Project In-field Facilities Pipelines Nuiqsut Landscape Change from 1955 to 1992, Central Colville River Delta
Floodplain Dynamics 1954 1981 2004
1982 Thermokarst Pits 1945 1982 2001 250 m 2001 Thermokarst Pits 2001 1.5 m pixels 93% (n=202) of easily visible large pits (>9 m 2 ) in 2001 not evident in 1982 Area increased from 1.0% in 1982 to 5.4% in 2001 0.6 m pixels
1945 Time Series: Beaufort Coastal Plain Drying location Wetting location
1982 Pond shifts Pond develops
2001 Ponds drains Pond develops Pond drains
1982
2001
Detection Depends on Resolution 0.6 m 1.6 m 0.6 m 1945 1982 2001
Extent of Ice Wedge Degradation Water-filled pits (red) in indicate recent degradation, 3.8% of area. Potentially could affect ~20% of area. ~20,000 thermokarst pits in study area Based on spectral analysis of waterbodies Photointerpretatio n Areas 3 x 5 km area
Permafrost Degradation Factors Mode Climate Warming Glacial Thermokarst Landscape Position Thermokarst Lake Groundwater Movement Collapse-scar fens Soil Texture Collapse-scar bogs Ice Morphology Collapse-scar pits Ice Content Mixed Pits & Polygons Water tracks & Gullies Piping with Pits Mounds &Hummocks Nonpatterned Size ha km 2 ha km2 ha km2 m ha m m m ha m m n/a
Remote Sensing Sampling Design Systematic point sampling with post- stratification by ecological components 9 Transects 1000+ pnts every 10 km 1 x 1.5 km photo
Airphoto 1 X 1.5 km, 0.3 m resolution Boundary of 200 x 200 m interpretation area Landsat View Data entry form with dropdown lists Enlargement of Centerpoint
Extent of Thermokarst in the Discontinuous Zone in Alaska Thermokarst Extent Thermokarst Modes Unfrozen Initially 26% Unknown 20% Thermokarst 7% Frozen 47 % Thermokarst Pit 7% Collapsescar Bog 7% Collapsescar Fen 46% Glacial Thermokarst 13% Thermokarst Lake 20% Thermokarst Basin 7%
Geomorphic Relationships Areal Extent (%) 4 3 2 1 0 Ice-cored moraine Thermokarst Pit Collapse-scar Fen Collapse-scar Bog Thermokarst Basin Thermokarst Lake Glacial Termokarst Lowland Loess Abandoned Meander Fl... Organic Fen Ice-poor Thaw Lake Margin Deep Thermokarst Lake Area Extent (%) 25 20 15 10 5 Initially Unfrozen Nonpatterned, Unknown Nonpatterned, Frozen 0 Bedrock, Exposed Residual Soil Weathered Bedrock Hillside Colluvium Talus Retransported Old Moraine
Thermokarst Mapping
1954 Vegetation Change
2004
1954 Vegetation Change
2004
1978 1995
5 0.0 4 5.0 4 0.0 3 5.0 3 0.0 1949 1978 1995 2 5.0 A r e 2 0.0 1 5.0 1 0.0 5.0 0.0 L o w l a n d L o w S c Lowland Black Spruce Forest Lowland Mixed Forest Lowland Birch Forest Lowland Fen Meadow E c o s y s t e m T y p e Lowland Bog Meadow Lakes or Ponds Total Degraded Area
1949 1995 Lowland Low Scrub (21%) Lowland Black Spruce Forest (11%) Lowland Mixed Forest (7%) 1% 4% 1% 1% 9% 9% 11 % 3% Lowland Low Scrub 0.3 % Lowland Black Spruce Forest (24%) 1% Lowland Mixed Forest (9%) (4%) How much of each ecosystem type? What changed into what? Lowland Birch Forest (23%) 14 % Lowland Birch Forest (15%) 7% Lowland Fen Meadow (31%) 31 % Lowland Fen Meadow (40%) (7%) Lowland Bog Meadow 1% 7% 0.3 % Lowland Bog Meadow (7%)
1918 Near Naknek River, King Salmon P. Hagelbarger
2005 G. Frost
1918 Near Naknek River, King Salmon P. Hagelbarger
1919 Photo by J. Sayre, National Geographic Overlooking area between Lake Grosvenor and lower Savonoski River in 1919 (J. Sayre) and 2005 (T. Jorgenson). Trees and shrubs have overgrown most of the rock outcrops visible in the original image. A lake bottom (far right background) has also drained and become vegetated. Absent in 1919, crustose lichens are now conspicuous on the rocks around Sayre s toppled cairn. This almost certainly represents recovery after disturbance rather than expansion. A possible cause of lichen mortality was acid rain following the eruption of Novarupta in 1912. 1919 photo courtesy National Geographic Society.
2005 Jorgenson
1919 Photo by J. Sayre, National Geographic Overlooking area between Lake Grosvenor and lower Savonoski River in 1919 (J. Sayre) and 2005 (T. Jorgenson). Trees and shrubs have overgrown most of the rock outcrops visible in the original image. A lake bottom (far right background) has also drained and become vegetated. Absent in 1919, crustose lichens are now conspicuous on the rocks around Sayre s toppled cairn. This almost certainly represents recovery after disturbance rather than expansion. A possible cause of lichen mortality was acid rain following the eruption of Novarupta in 1912. 1919 photo courtesy National Geographic Society.
Issues with Using High-res Creating time series (availability, quality) Spatial control (ground, image to image) Co-registration accuracy Whole photo versus subset Resolution differences, minimum detactable change Spectral differences (color, B&W), Interpretation (knowledge of interpreter) Sampling (polygons, lines, circles, points) You need a lot of class! (i.e., classification, what are you detecting)
SUMMARY ADVANTAGES High-resolution has a wide range of applications Can assess changes in small features Practical for time-series going back 50+ yrs Manual interpretation for multiple components DISADVANTAGES Limited availability Limited coverage Manual interpretation, consistency