Thank you for bringing up Copernicus EMS and HDDS, I've added it to my observation notes. That data would be definitely be useful, but no one in the effort knew about these resources at the time.
Water rescuers were given a general idea of an area that could be assumed flooded throughout, but boaters had to exercise caution at all times because of water hazards (both stationary and mobile) and flood waters could subside without warning, leaving some boats stranded on shallow mud flats.
While it was somewhat life-threatening with water rescues, the lack of data could be worked around because the water rise to the point it was life-threatening was reckoned in 15-30 minute intervals, and people could coordinate rescues of rescuers around that timeframe. However, in a fire response version of such Net-based coordination, accurate, up-to-the-second assessment would be life-critical. Not sure how to address that without industrial-grade drones or even UAV's, and hella-expensive grade FLIR, and the FAA (and possibly DHS) would then be deeply involved.
Not sure why UAV-based realtime GIS mapping wasn't deployed. The hardware tech exists, but perhaps the pipeline for data ingestion, cleanup, processing and publishing isn't up to realtime demands, even for a limited scope of "show me what is different from this satellite GIS map of the same area". That would be an interesting problem to solve, correcting for daylight shadows, transient objects like cars and planes, etc.; I'm sure the military intelligence folks in the IMINT sector have long since worked out the initial challenges of this problem space, but open algorithms for applying to this problem space (not to speak of code) don't seem readily available to me after searching around, so it might be a long slog up the learning curve.
These disasters might be a good application of temporary air mobile vehicles supplying some form of wireless signal. If you're going to loft up a vehicle into the air to collect realtime GIS, you might as well blanket the area with an emergency wireless signal. Would have to solve problems around rate-limiting, dynamic prioritization based upon confirmed emergencies, etc.
The flooding points out to me the lack of research into flood waters diversion [1]; there is still a lot we don't know about what happens when we try to mitigate excess flood waters. We know at least some flooding is necessary for managing topsoil erosion. But even the $26B estimate to bring Houston up to a more hardened flooding posture [2] seems like cheap insurance compared to the $100B estimates being thrown around now. I've wondered if it is possible, and what it would take to build a national water grid that intakes excess flood waters in one region of the nation, processes it so it is ecologically "clean" of invasive species, and shunts it to a drier region. The capacity of such an infrastructure within the channels themselves might lessen the need for designated floodwater storage plains, and simultaneously vastly increase land utilization. However, megascale infrastructure projects still seem out of our grasp in this era.
[1] https://www.sciencedaily.com/releases/2016/01/160106114744.h...
[2] https://www.theatlantic.com/technology/archive/2017/08/how-m...