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LC-07 Abstract

Multi-Scale Analysis of Inundation with Microwave and Optical Remote Sensing in the Amazon Basin: Applications to Biogeochemical Measurements and Modeling

Bruce R Forsberg — INPA - Instituto Nacional de Pesquisas na Amazonia (SA-PI)
John M. Melack — University of California, Santa Barbara (US-PI)
Evlyn Novo — DSR (INPE) (SA-PI)

We propose to conduct a multi-temporal, multi-scale, multi-sensor analysis of

inundation and wetland vegetation in the Amazon basin that will be linked to

biogeochemical measurement and modeling activities of LBA.

Our proposed remote sensing analyses will include optical (Landsat, AVHRR and EOS

sensors), passive microwave (SMMR/SSMI) and active microwave (SIRC, JERS, ERS, and

Radarsat) data to determine the temporally varying extent of inundation and associated

vegetation. We will (1) provide synoptic, seasonal mapping of inundation and wetland

vegetation structure for the Amazon basin; (2) incorporate the inundation and vegetation

data into a GIS-based database; and (3) apply results from our analyses of wetland

vegetation and inundation to related LBA studies of hydrological, ecological, and

biogeochemical processes.

The expected time periods for recording an image useable for inundation analysis with

the different remote sensing instruments we propose to employ varies from days to months.

Based on an analysis of the spatial and temporal resolutions of the satellite sensors, we

have determined that data fusion amongst the instruments will be critical to insure

sufficient temporal coverage at the appropriate spatial scales. We anticipate that there

will be an inundation-mapping limit for typical rivers with contributing drainage basins

on the order of 1000-10,000 km2 when the flood conditions occur only for a week to a

month. Individual sites may be mappable above and below this limit, depending on the local

geomorphology and inundation hydrology.

We anticipate results of our analyses to be important for LBA activities associated

with (1) methane and other trace gas emissions, (2) carbon dynamics of flooded forests,

(3) land use on flood plains, (4) regional hydrologic modeling, and (6) detection of

seasonal and inter-annual climate variability.


Implementation of our activities will be done as follows:

Optical sensing - The most effective technique for tracking the zone of river-water

influence, in contrast to local-water influence, on wetland inundation is through the use

of optical data of sufficiently fine resolution. We will modify our current method for

suspended sediment analysis to incorporate data from the optical instruments expected

during LBA, i.e., Landsat 7, MODIS, and AVHRR. The optical image analysis will be limited

by access to sufficiently cloud and smoke-free data.

Active microwave sensors - We plan to use a multi-stage, hierarchical, rules-based

approach to delineate floodplain inundation and vegetation using a decision-tree model

which constructs a binary classification tree by recursively partitioning the training

data into increasingly homogeneous subsets. Inundation mapping at a fine scale (12.5 m to

100 m pixel spacing) will be carried out using a combination of JERS (LHH), Radarsat

(CHH), and ERS-2 (CVV) data. All these data will offer multi-temporal coverage of selected

regions; only Radarsat's ScanSAR is expected to provide multi-temporal coverage of the

whole Amazon basin during LBA.

Passive microwave sensors - Low-resolution sensors, such as the Scanning

Multi-channel Microwave Radiometer (SMMR) and the Special Sensor Microwave Imager (SSMI),

afford a synoptic view of the Amazon basin that complements finer-resolution SAR and

optical data. We have developed linear mixing models that incorporate the observed

microwave signature's major end members to estimate fractional inundation area. Data will

be obtained as 0.25° x 0.25° grid cells, and modal values for each 2-week period will be

used to determine inundation area 

Field studies - Field surveys will be required at key LBA sites and selected

wetlands to validate our classifications and maps. These surveys will entail low altitude

videography and surface inspections from land and water. Geo-location of flight lines and

surface sites will be done with portable GPS units. Further, we will use information

obtained from the many hours of low altitude videography and field observations that we

have collected previously, as well as from published literature and from personal

contacts. To improve correlation between water levels and inundation extent in wetlands

distant from major rivers or gauging stations on rivers, we will install automatic water

level recorders.

Projected Schedule

During the first year, we will emphasize extension and validation of our microwave and

optical classification algorithms and assembly of mutli-temporal data sets from ERS,

Radarsat, JERS, Landsat and SSMI acquisitions. During the second and third years, we will

emphasize production and distribution of inundation and wetland vegetation maps to

relevant LBA projects and for our own complementary analyses.

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