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  • Product Sheet: Wet areas

WET AREAS

Image credit: Hatfield Consultants

PRODUCT DESCRIPTION

Category

Component products

Land Cover

N/A

Uses

  • Surface Geology Mapping - Terrain evaluation and geo-morphology characterisation
  • Seismic Planning - Identification of adverse terrain for trafficability
  • Seismic Planning - Areas of poor coupling
  • Subsidence monitoring - Infrastructure monitoring
  • Environmental monitoring - Baseline historic mapping of environment and ecosystems
  • Environmental monitoring - Continuous monitoring of changes throughout the lifecycle
  • Environmental monitoring - Natural Hazard Risk Analysis
  • Logistics planning and operations - Facility siting, pipeline routing and roads development
  • Logistics planning and operations - Support to surveying crews for planning surveys and H&S

Geo-information requirements

  • Water quantity identification
  • Terrain information
  • Topographic information
  • Detailed land use information
  • Detailed land cover information
  • Lithology, geology and structural properties of the near surface

Description

EO data offer a cost efficient method for identifying and monitoring wet areas.

Optical sensors can effectively delineate herbaceous/open wet areas based on distinctive spectral characteristics and spatial heterogeneity.

Radar sensors can effectively identify wet areas, and may compliment optical data, or provide unique information. Mapping marshes or wet areas under tree canopy can benefit from radar data. Radar backscatter is sensitive to dielectric properties (soil and vegetation moisture content), geometric (surface roughness) attributes of wet area surfaces, and presence of standing water. Longer L-band wavelength provide better penetration of forest cover to determine wet or flooded status of the ground surface. Shorter C-band based wavelengths provided information for herbaceous wet area detection. L- and C-band data are needed to separate forest from herbaceous wetland as well as from other land cover.

Archived optical and/or radar data can be used for historical mapping of wet areas in comparison with current conditions. Taking into account that wet areas may be ephemeral and not present during baseline data acquisition, multi-temporal data (particularly radar) may reveal seasonally wet areas.

Modelling of the terrain and prediction of potentially wet areas is valuable. Depending on the scale required this can be achieved using satellite-derived elevation datasets of various resolutions. The use of elevation data derived drainage provides improved scope for localisation of ephemeral wet areas, which appear after long period of rain or with higher than usual groundwater levels.

The wet areas product delivers maps showing the location and extent of wet areas (e.g., marshes, ephemeral wet areas).

Known restrictions / limitations

Historical wet area mapping depends on the available archive of images, and optical images may be affected by cloud cover. A potential limitation with wet area extent products is the presence of dense forest vegetation within the water/wet areas, and in some systems where water levels and extent can change considerably (e.g., marshes). Longer wavelength radar sensors (e.g., PALSAR-2 with L-band) mitigate this issue to some extent.

The real resolution of radar data and products may be reduced due to effects of image speckle and the need to filter images and output products.

Prediction of ephemeral wet areas is dependent on the availability and quality of DEMs – mapping of subtle changes in elevation may require elevation data with accuracy that can be obtained using LiDAR.

Wet areas extent is connected to surface hydrology and groundwater levels; wet area modelling should take these factors into account.

Lifecycle stage and demand

Pre-license

Exploration

Development

Production

Decommission

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Pre-License: Information on existing wet areas is important early in the evaluation of a prospect.

Exploration: Wet area mapping supports the effective management of environmental sensitivities as well as the movement of equipment and people. Knowledge of wet areas can also contribute to more effective land seismic survey.

Development: Information on wet areas extent (wetlands, lakes, etc.) supports the environmental impact assessment for development and effective management and mitigation of impacts.

Production: Information supports water management for operations, including appropriate environmental setback distances.

Decommissioning: Information supports water management for decommissioning.

Geographic coverage and demand

Coverage and demand is global, but of particular utility in less developed countries or for remote areas.

Challenges Addressed

OTM:016  Identification of seasonal obstructions to logistics activity

OTM:017  Identification of seasonal environment changes e.g., migration patterns

OTM:030  Ecosystem valuation of potential site

OTM:036  Geohazard exposure analysis

OTM:038  Planning secondary surveys

OTM:042  Identifying seasonal terrain changes e.g., for access

OTM:045  Identifying soft ground for seismic vehicles

OTM:065  Floodplain mapping

HC:1103  Identify soft and hard ground as areas of potentially poor source and receiver coupling

HC:1202  Identify rivers, lakes and wet areas to apply safe setback distances

HC:1203  Identify areas with soft sediments to plan access and assess hazards

HC:3204  Monitor stability of surface reservoirs such as settling ponds

HC:4303  Understand extent of lakes and wet areas for hazard assessment

PRODUCT SPECIFICATIONS

Input data sources

Optical: VHR1, VHR2, HR1

Radar: HR1, HR2, MR1

Supporting data:

  • Digital elevation models (DEM)
  • Existing GIS data such as topographic maps, infrastructure, and assets
  • Local knowledge
  • Precipitation and groundwater information

Spatial resolution and coverage

Spatial resolution: 0.5–10 m

VHR1, VHR2, HR1, HR2 depending on the desired coverage (Regional, Basin, or Project level).

DEM vertical resolution should fit to the reflectance data, which in the case of VHR1 and VHR2 may require obtaining it from other sources (local databases, SAR, LiDAR).

Minimum Mapping Unit (MMU)

Variable, depending on source data resolution.

If raster-based products are delivered the product is constrained by the elevation model pixel resolution.

Accuracy / constraints

Thematic accuracy: 80-90% in areas of low vegetation cover and density.

Spatial accuracy: The goal would be 1 pixel, but depends on reference data.

Accuracy assessment approach & quality control measures

Comparison with ground based observations.

Frequency / timeliness

Observation frequency: Dependent on the radar sensor and beam mode (resolution/extent) selected. Frequency of historical maps is highly variable depending on the archive.

Timeliness of delivery: Delivery time need not be rapid, but data will be required before specific project phases, e.g., before exploration and development, and prior to or coincident with decommissioning.

Availability

On-demand availability from commercial suppliers.

New acquisitions can be requested globally.

Archived products available for public search. Availability may be limited for specific dates and locations.

Delivery / output format

Data type:

  • Raster
  • Vector (depending on customer needs)

File format:

  • Geotiff
  • Shapefile or any other OGC standard file formats

 

 Download product sheet.

 

Lead author:

HR/SRC

Peer reviewer:

OTM/GeoVille

Author(s):

Dean, Aleksandrowicz

Document Title:

Wet Areas

# of Pages:

4

Circulation:

Internal – Project consortium and science partners

 

External – ESA

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