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outflow of downstream conditions. Moving boundary problems were treated
by applying a threshold technique, where a thin water depth is reset in dry
nodes of all moving boundary elements every time (refer Ref. 3 for more
detail).
4. Assigning Elevations of Main Roads, Dikes, and
Road-Opening Works to FEM Domain
The elevations of those construction works that have a significant influence
on flow regimes in the study area were assigned to FEM nodes and elements
in the model simulation (see Fig. 1). Construction works were selected based
on the “Road Opening Survey” report of Mekong River Commission
2
and
other available data, and included NR1 (National-Road 1) from Phnom
Penh to the Vietnam border; NR5, NR6, and NR7; a local road on the
left bank of the Mekong River, from Khsach Kandal to the junction with
NR11 at Ta Kao; dikes on both sides of the Mekong River from Kompong
Cham to near Tan Chau; dikes of the Tonle Sap River from Phnom Penh
to Prek Dam; dikes on both sides of the Bassac River, from Phnom Penh to
near Chau Doc; and main road-opening works located on the selected roads
and dikes. Arc-GIS tool was used to convert the polyline shape data of the
selected roads, dikes, colmatages, which are a facility of French technology
to lead river water into areas behind the levees, and road-opening works to
point data. Co-ordinates of these points were used to find the FEM nodes
closest to the points, and the elevations of the selected roads, dikes and
road-opening works were then assigned to those FEM nodes.
Fig. 1.
Assigning elevations of the selected roads, dikes and road-opening to FEM nodes.
