I have received an Hecras 1 dimension model. Basically, there is an old existing bridge which needs to be replaced with a new one. The bridge and the approach road has been located on the flat flood plain (0.05%)(My first question do you think this slope is flat?). The new bridge is has smaller opening so we need to build a relief structure under the road next to the bridge to protect the road against the flooding.
Something like this :
https://www.civilgeo.com/knowledge-base/modeling-hec-ras-multiple-bridge-openings-as-divided-flow/
I have model this with a bridge and a culvert under the road in the floodplain.( The flood plain is divided into two flood plain by the small bump which is located in the middle of the floodplain)
The extend of my XS are 700 m(The flood for more than 1 in 20 years is spread out to 3 km).
I have calculated the peak floods by Flood frequency analysis for different return periods) and ran the model in steady state. The flow is quite high Q2 = 280 m3/s … Q100 = 4629 m3/s.
My first cross section is at change 100 and the last one 800. (The length of my network is just 700 m)
My questions are :
1- Is it ok to model this bridge in 1 dimensional hecras model or I need to model it in 2 d model?
2- There is no hydrological model available for this area. I just have the peak flow. I need to change the peak flow to hydrograph. Ho can I do that?
3- Is the extend of my model enough for this study (300 m upstream of the bridge and 400 m downstream of the bridge length is 150 m)
Thank’s