An integrated hydro-topographic model for Viti Levu Gau Conway
Pene 2012 Pacific GIS&RS Conference 27-30 November 2012,
Suva
Slide 2
Hydro-topo integration Water flows downhill... Hydro surface
water, stream network... plus... Topo surface shape, slope and
aspect... equals... A catchment model
Slide 3
Test site Gau island, central Fiji
Slide 4
The big picture 1.Create a Digital Elevation Model (DEM)
2.Process the DEM to find breaklines Streams and ridges 3.Create
hydro network Logical network junctions, streams, catchments
4.Integrated model for hydro flow analysis
Slide 5
Step 1 - DEM using terrain-specific tools Traditional terrain
data Contours, spot heights, cliffs PLUS Hydrological data Streams,
lakes, sinkholes Hydrology easy to follow on air photos, thus
higher accuracy hydrology enforce the terrain shape i.e.
breakline
Slide 6
Need to do some cleaning first...
Slide 7
Completed DEM
Slide 8
Step 2 Process DEM DEM Flow direction from each cell to next
(slope) Flow accumulation Stream segments (accumulation threshold)
Catchment boundary
Slide 9
Flow directions
Slide 10
Flow accumulation
Slide 11
Stream segment
Slide 12
Catchment boundary
Slide 13
Step 3 Hydro network Convert raster from DEM processing Stream
segment to vector line network Catchment boundary to vector
polygons Points created at stream junctions
Slide 14
Stream segments
Slide 15
Catchment polygons
Slide 16
Network junctions
Slide 17
Flow tracing using the model
Slide 18
Runoff calculation Predict volume of water at end of catchment
Amount of rainfall Size, shape, slope of catchment Surface
characteristics (vegetation, soil)
Slide 19
Amount of rainfall WorldClim climate raster
Slide 20
Catchment characteristic Curve number hydrological parameter 0
100% of rainfall runoff Function of land cover and soil type Land
cover vegetation layer Soil type made up (no soils layer for this
island)
Slide 21
Vegetation + soils
Slide 22
Curve number
Slide 23
Curve number x rainfall = runoff
Slide 24
Clip runoff to a catchment
Slide 25
What next?... Apply to larger island (Viti Levu) Heavy data
load for desktop computer Calculate realistic curve numbers Make
dynamic runoff query tool Hover over map and pop-up runoff
value