In This Space
Hydrological network & catchment area
Lake Chad basin & hydrological network 2013 (Source: GeoVille)
☒ Integrated Product
This product provides information on the hydrological network and the catchment area by combining various types of topographic data (elevation, slope gradient and direction). Thus, the current and future, hydrological driven, utilization potential of the surrounding land based on satellite data can be estimated. Furthermore, information on the hydrological network and catchment area helps to identify potential areas of flooding.
A hydrologically correct elevation data set is generated by ensuring that surface features such as vegetation and buildings are removed (bar earth) and filling unwanted or incorrect sinks within the elevation data. The Elevation data is used to calculate the direction of water flow for each pixel of the input data. This flow direction information is used to calculate accumulated overland flows, which are used to derive hydrological networks (streams/ watercourses). Further GIS operations are used to generate a hydrological network with stream orders (e.g. Horton-Strahler stream order). Streams can be defined by the number of cells draining into one cell. This information is used to delineate catchment and sub-catchment areas.
This product delivers PDF maps or vector or raster digital files that delineate and identify:
These products can be used as an input for hydrological modelling, to derive e.g. sheet flows on plains or for modelling of potential flood areas for flood risk assessment.
Known restrictions / limitations
The main input for this integrated product is an elevation model, which can be based on radar or optical data. By using optical data a higher resolution can be achieved (there are more and higher resolution optical VHR sensors than radar sensors), but the restrictions of optical data concerning cloud coverage in areas with high cloud cover (e.g. inner tropics) have to be considered.
Furthermore, high latitudes coverage is restricted. When generating DEM from stereo pairs, good quality imagery needs to be available with 2 or more images showing the same area from different directions. This can be a time consuming process. Lower resolution DEM data is available off the shelf.
An important issue is the DEM is used to estimate surface flows, and in many regions the hydrology is influenced heavily by geology and surface flows, particularly in sedimentary geological regions (e.g. Karst).
Lifecycle stage and demand
Exploration, Development & Production:
Geographic coverage and demand
Demand and coverage is global.
HC:2102 Understanding hydrogeology
Input data sources
Optical: VHR1, VHR2, HR1, HR2
Radar: VHR1, VHR2, HR1, HR2, MR1
Spatial resolution and coverage
Spatial resolution: 0.5 - 90 m pixel size
Minimum Mapping Unit (MMU)
n/a (the product is directly based on the input data; the smallest unit is one pixel)
Accuracy / constraints
Thematic accuracy: 70-90%
Spatial accuracy: The goal would be one pixel, but this depends on reference data
Accuracy assessment approach & quality control measures
Stratified random points sampling approach utilizing in-situ measurements. Statistical confusion matrix with user’s and producer’s accuracy as well as kappa statistics for hydrological network and catchment area mapping.
Frequency / timeliness
Frequency: The frequency is constrained by satellite revisit and acquisition timeframe, but also processing requirements. Depending on the requirements of the customer the best suitable satellite sensor has to be chosen considering spatial / spectral resolution as well as revisit frequency and timeliness. For coarser resolution DEMs, static products exist for most parts of the globe.
Timeliness of deliverable: As fixed models are used for production, the product can be generated within a day if the area does not exceed certain boundaries.
Freely available or commercially acquired depending on the sensor selected.
1 km, 90 m (most common) and 30 m DEM are freely available from SRTM version 3 and Aster GDEM2 for higher resolution this is a paid for data set. These data sets for example are Elevation 30 (SPOT DEM 30 m), WorldDEM (TanDEM-X 12m), Elevation 8 (SPOT DEM 8 m), Elevation 4 & 1 (Pleiades DEM 4 m & 1 m), WorldView Elevation Suite (1 m).
Delivery / output format
|Peer Reviewer:||Hatfield Consultants|
Maria Lemper, Jan Militzer
Hydrological Network & catchment area
# of Pages:
Internal – Project consortium and science partners
External – ESA
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