Yes, it's all hypothetical because levee has not broken and there's not really any reason to think it will break, just something they're watching carefully.
If the flow were to go into parts of Lava Tree park, then the flow would proceed just east of Nanawale. Don't look at google maps. Look at a topo maps and you can get much better idea of actual topography, for example: https://ngmdb.usgs.gov/img4/ht_icons/Browse/HI/HI_Pahoa%20South_349642_1994_24000.jpg
That's an excellent topo map, thanks for that. But it also shows the ridge north of Lava Tree. Since this is a US map, I'll assume that these are feet; it shows that the ridge is 40-60 feet high. Do you think it would go to flow over a 40-60 foot ridge? Or over the lava flow that's met up with the ridge on its eastern end? I'm just trying to understand what you're picturing. I can see that as a possibility, but it's not to me obvious that that's the easiest path downhill, for lava starting in Leilani at the height of the ridge line. It certainly would be if the north lobe hadn't already butted up against the ridge...
A big unknown, at least for me, is the thickness of the flow in the north lobe at that point. If it's not that thick, then it's not much of a barrier.
And yes, I'm glad that this is all hypothetical at this point
All the geologists are saying there is no sign of letup.
They've noted a reduction in flow rates, as indicated by fountain heights, at several points in time. It's been mentioned in some of the USGS videos. As of 3 days ago, they were talking about it varying from 130 to 230 feet. It used to be a sustained 250 feet. So long as flow rates keep declining, that will reduce it's ability to flow such long distances away from the fissure. Of course, I have no ability to say whether it will continue declining as such, only to note that that's the general trend of volcanic eruptions.
The big danger is not for Nanawale, but for the rest of Leilani. Fissures 9 and 10, which are uprift of current flow have been gassing and there has been some incandesence, and they could go off again. I hope that does not happen because if that happened a much larger part of Leilani residential area would be destroyed.
Not at all to downplay the danger to the rest of Leilani. I certainly have no ability to say what's going to happen underground. All I can say about the lava is, whenever it's on the surface, it will move downhill - up to the point that it cuts off its own path to move downhill, or something else does. Wherein it'll emerge "somewhere else" and flow downhill from there. That's just what lava does
Even if 9 and 10 don't reactivate, there's a serious risk of new flow lobes at some point in the future within Leilani, walled off by previous lobes from taking the easiest route to the coast.