FMA Challenge 3: Difference between revisions

The image below shows the flood depths and extent for the two non-infiltration simulations at 100ft resolution (left with channel 'n' = 0.2, right with channel 'n' = 0.1). Some significant deviations in flood extent can be observed, particually soth of the main channel. This can be largely attributed to the higher conveyance in the channel for the 'n'=0.1 case. <br>

[[File:FMA3_3.jpg|600px]][[File:FMA3_4.jpg|600px]]<br>

The effect of channel roughness can also be seen in hydrograph outflows from the model downstream boundary. Of particular interest is that reducing the n value to 0.1 has a significant effect on the arrival time of the flood waters at the model outlet (much earlier), and reduces the volume of water flowing onto the floodplain by around 20% due to the higher conveyance of the creek. Also of interest is that for the n=0.2 scenario, some overbank floodwaters return to the main creek near the model outlet causing a delayed second rise in the outlet flow hydrographs as illustrated in the chart further below. This effect does not occur for the n=0.1 scenario, with all overbank floodwaters remaining on the floodplain.<br>