RHESSYS FOR SANDHILLS REGION OF NORTH
CAROLINATom CravenMatt SimonAnne Trainor
Objective Construct a RHESSys ecohydrologic
model for Sandhills Region
Sandhills Eight-County Area. Shown on a blue to red color ramp is an 20 foot elevation model of the region. Dashed black lines indicate primary roads, blue lines - major hydrology. Ft. Bragg (right) and Camp Mackall (left) boundaries are shown in fuchsia.
Study AreaThe Sandhills, NC
Study AreaSandhills Vegetation and Critters
Sub-basin – Cape Fear 14, Part of the Cape Fear River Basin
DataSub-basin
DataCatchment Topography – Flat Creek Watershed
DataCatchment Elevation – Flat Creek Watershed
DataCatchment Soils– Flat Creek Watershed
DataWetness Index– Flat Creek Watershed
DataMet and Stream Data
DataMet and Stream Data
MethodsArc Hydro Delineation
The entire sub-basin was processed using Arc
Hydro in ArcGIS 9.2 using a LiDAR-derived digital elevation model (DEM) created from the North
Carolina Floodplain Mapping Program
(NCFMP) by the North Carolina Department of Transportation (NCDOT
This DEM has a 20 ft spatial resolution or roughly 6 meters.
MethodsReclassified LULC from 15 to 4
classes– Hardwood
• Deciduous Forest• Shrub/Scrub• Woody Wetlands
– Evergreen• Evergreen Forest• Mixed Forest
– Open/Barren• Developed (open space, low and
medium intensity)• Barren
– Herbaceous • Grassland• Herbaceous• Cultivated Crops• Emergent Herbaceous Wetlands• Open Water
MethodsLand Use Type 30 m pixels Percentage Cumulative %
Evergreen Forest 11623 50.57% 50.57%
Grassland/Herbaceous 4003 17.41% 67.98%
Barren Land (Rock/Sand/Clay) 3431 14.93% 82.91%
Woody Wetlands - Deciduous 1796 7.81% 90.72%
Developed, Open Space 1228 5.34% 96.06%
Developed, Low Intensity 277 1.21% 97.27%
Deciduous Forest 248 1.08% 98.35%
Mixed Forest 238 1.04% 99.38%
Shrub/Scrub 114 0.50% 99.88%
Cultivated Crops 12 0.05% 99.93%
Emergent Herbaceous Wetlands 6 0.03% 99.96%
Open Water 6 0.03% 99.98%
Developed, Medium Intensity 4 0.02% 100.00%
Totals 22986 100.00%
Methods Arcview (Arc2World) to construct world
file Template File Parameters
Single Soil Type: Sandy Loam Land use: Undeveloped 4 Vegetation Types from 30 m LULC Topography
DEM, Hill slope, Wetness index, Slope, Aspect Patch Identification
Composite of hill slope, wetness index and LULC Trial 1: 4,161 discrete patch ids
Raster calculator: LULC + WI*100 + hill slope * 100000
Trial 2: 91 discrete patch idsRaster calculator: LULC + WI*10
Model Output
Future Steps
Get the model running Incorporate variation in soil types and
depths Use explicit routing to examine
hydrologic connectivity
Newbie User Reflections Add option to write a logfile with state
variables Examine templates and create worldfiles
in class for the example watershed Initial gray areas
Exact method for creation of useful grids Headers in .def files
Going from scratch was difficult but yields a better understanding of the inner workings