I'm pretty sure I stumbled on a map that was linked through an article I read before we left. I believe the article linked to HarveyRelief or HarveyRescue. It may have been a Buzzfeed article like this one:
https://www.buzzfeed.com/maryanngeorgantopoulos/crowdscourin...
The maps are down now as I believe the website went dark once the main flooding danger in Houston was past.
The map appeared to show markers all over the Texas Coast color-coded based on the type of request. The user was able to select a marker and in the left pane a descriptive entry gave information about the address, the number of people requesting rescue including a breakdown of #adults versus #children or elderly. Many posts had telephone contact numbers and each one had an entry from the person requesting assistance granting permission to post their request. Something like an "I Agree" entry after their contact info in the post. I visited the website while it was up and looked at the help request submission part and it was a pretty simple dialog set collecting the needed information along with an "I Agree" or a "Yes" button at the end granting the website the permission to post.
Early problems were predictable. Some of the posts should have been expired because the people had been rescued. Handling the updating of the information required the rescuers to confirm that the people had been rescued so that marker could be cleared. We ended up following several leads that had to be from the previous day. When we arrived at the target address the streets were dry, families were walking pets and kids were riding bikes in the street in one case. A couple of others also involved places where waters had receded and one involved a non-existent address that turned out to be along the beltway between two businesses.
The website did clear many of the older posts and altered the color-coding so it would be clear what you were heading for - medical problem needing assistance, people trapped needing rescue, etc.
It was quite handy. I know there were other maps including one maintained by the Cajun Navy that was similar to the one we used.
There is room for improvement in the maps and in how they coordinate with rescue assets. Timeliness is important and older posts in neighborhoods known to be heavily visited by rescuers should be cross-checked using contact info provided. A lot of traffic on the Cajun Navy channels was people confirming that a rescue needed to happen or that one had already occurred for a particular address.
I believe that the actual requests for assistance on the map I used came from those needing the help since many of them were from someone who was posting for a person needing help who had no access to phone or other communication network. I don't know who had the ability to remove the markers once they were placed but I know that feature by itself needed improvement in tracking rescues that had already occurred.