Ketaki Agrawal Junior Research Fellow

Hi,

I am a new user to MIKE software and am using it for creating flood inundation maps. As a beginner, I have started with MIKE 11 and have been partially successful so far.

Please refer the attachment for better understanding of my query.

There is an image file of my area of interest, Digitized river network and cross sections, flood inundation image.

Branch 1 is the main river channel, which bifurcates to Branch 5 in the downstream side which is the flood plain area. Branch 2 and Branch 3 are the joining rivers.

1. I need to confirm the rules for digitization of river network , i.e, in my case, I have digitized the Branch 1 till the end,  then joined the tributaries and the Branch 5. So wanted to know if this way of digitization is appropriate or there can be a other alternative?

2. the cross section spacing? Since, the study area is very big around 300 km, I have taken 2000 m as spacing.

3. I don't understand the concept of alignment markers. Like, is digitization of these make any difference? In my case , there aren't any kind of structures in the study area.

***4. Boundary conditions- This is where am stuck. I have time varying discharge and water level data at the U/S end,i.e Branch 1 , 2 and 3 ,hence using open ,inflow boundary conditions at these places.
But, I don't have any data at the D/S end. so I have assumed constant water level based on the cross sections, since the dem I use is very precise.

I was advised to opt for Q-H boundary condition but I dont know why, the "auto calculation of q-h" tab does not pop up when clicked. kindly help me figure that out.

5. The Manning's n value. We give n value in the cross section editior and also in the HD parameters dialog. Since, changing n value  at one place doesnt effect the other, Please help me understand which one effects the simulation.

6. Last question is , the flood map does not match the requirements near the flood plain area, as in the water spread is very bizzare. I have tried a number of times, by changing the cross section spacing, but no positive results. Also the water depth is very less in the flood plain area.