[emilyrose]

Thank you so much for your reply!

My thesis is assessing the hazard of a potential glacial lake outburst flood, so the rest of my thesis has assessed how the hazard has changed over the past decade, i.e. glacier area change, lake area and volume change etc., I have also assessed how the vulnerability of the downstream community has changed in terms of population and infrastructure at risk. So the final step would be to tie this together which an estimation of how far an outburst of that size may travel etc.

You are completely right, it is a lot to learn and I have very little knowledge on river hydraulics and flood modelling unfortunately, and neither does my supervisor but it is something I am being advised to do nonetheless – so I have been trying my best to teach myself the basics to complete this but it is rather complex to me.

Most research within the field does use a dam-breach model, however, these are more complicated and as the aim of my project is not to assess how the dam would breach I was hoping to do something as simple as possible. In terms of terrain, I have a modern DEM which I have produced a DTM in TIN format from (not sure if this is right), but using HEC-RAS I created a terrain from this which seemed correct.

I have currently been doing a 2D unsteady flow simulation, using a flow hydrograph for the upstream, and normal depth for downstream. As a moraine-dammed lake it is assumed that flood discharge would increase linearly to a peak and decrease linearly to 0 m3/s over a time span equal to that of the rising limb – so the hydrograph is assumed to be triangular in shape as has been applied to other GLOF studies. The peak discharge was calculated using Qmax= 0.72V^0.53, a relationship developed for moraine-dammed lakes.

I managed to get this simulation up and running but even giving the hydrograph a duration of 8 hours the result in RAS-mapper is showing the flood to travel only ~30km downstream, when I want it to reach ~90km downstream to a large town. I am certain it would reach this far as there has been a flood from a nearby lake which reached the town that was a fraction of the size of the lake that I am modelling. I have no idea how to resolve this at all, I may have carried out the whole simulation out wrong but I am unsure how to make the flood continue further.

I hope this makes some sense! Thank you for your time.

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