FMA Challenge 1 (1D-2D linked): Difference between revisions
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==Information to Modelers==
Assignment of all parameters for this analysis are at the discretion of the modeler. A high resolution aerial image is provided so that land cover details can be inspected. Information on the problem definition can be found on '''
=Relevant Files=
It is up to the modeler's discretion to determine what GIS package to use, what text editor to use, and how to run their models (batch mode or
=Solution=
A sample solution has been presented, courtesy of BMT WBM.
==Cross Section Spacing, Grid Size and Mesh Element Size==
The modeling approach represented the in-bank area with 1D elements dynamically linked to a 2D grid domain to represent the overbank floodplain.
The 1D sections provided were used for the in-bank topography. The overbank (2D) areas were modeled using 10ft and 15ft resolutions. The 2D grid dimension (rotated) was 17,500ft by 8,000ft. A total of 87 cross-sections were used for the 1D in-bank domain.
Structures were modeled as a combination of bridges and culverts. For bridges, height varying energy loss tables were used based on the Hydraulics of Bridge Waterways (Bradley, 1978). For culverts, TUFLOW simulates all possible inlet and outlet controlled flow regimes with automatic switching between regimes. The calculations of culvert flow and losses are carried out using techniques from “Hydraulic Charts for the Selection of Highway Culverts” and “Capacity Charts for the Hydraulic Design of Highway Culverts”, together with additional information provided in the literature such as Henderson 1966.
The number of cross sections and mesh elements used are as follows:<br>
{| align="center" class="wikitable" width="50%"
! style="background-color:#005581; font-weight:bold; color:white;"| 2D Cell Size
! style="background-color:#005581; font-weight:bold; color:white;" width=50%| 1D Sections
! style="background-color:#005581; font-weight:bold; color:white;" width=50%| Active 2D Cells
|-
| 15ft || 50 || 87 || 286,434
|-
| 10ft || 87 || 643,565
|}
==Computational Domain Assembly==
TUFLOW directly reads GIS data layers to construct models. The layers used/created for Challenge 1 are:
<ol>
<li>A DEM TIN created from the provided terrain data (2ft contours) and exported to ESRII ASCII format as a 2ft DEM grid. When TUFLOW reads this DEM it interpolates the elevations onto the 2D computation grid.</li>
<li>GIS layers of cross-section locations and 1D network including structure details.</li>
<li>GIS land-use layer digitized in .shp format.
<li>GIS layer of 1D/2D interface lines along the left and right banks of the channels.</li>
All model inputs are independent of the 2D grid cell size, orientation and extent, allowing for different 2D resolutions, dimensions and orientation to be easily simulated.
Peak flood depths and water levels were exported to ESRII ASCII grids, and the flood extent was created by contouring the grid into a single region. Flows are outputted in .csv format and directly loaded into Excel. Profiles were created using the post processing utility TUFLOW_to_GIS and outputted into a .csv file.
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