I still see you are stuck on the idea that recreational boating somehow had something to do with the flooding. If at this point you still have that mentality, there is absolutely no amount of logic on this earth that can be presented that will change that. Because ample logic and discussion on how they system as a whole operates has been laid out pretty clearly on this very thread.
I'm not sure where you are going with "illegal sand pits" being a contributing factor to flooding. A couple of things - unless the sand pit has a crater about the size of Galveston Bay, it's not going to make any difference in the change in flooding characteristics. At least not to an appreciable degree - there may be a change when you get to the 17th decimal place in your calculations. If anything, it would help because it provides additional capacity to store water before it goes downstream. So you'll have to clarify what you mean in terms of this bullet point as a contributing factor.
And honestly, any operation that has the potential to impact riverine systems doesn't just happen. ACE is involved, TCEQ is involved. A few other alphabet agencies that require beaucoup paperwork to make any modifications to any part of the valley below oridnary high water mark are involved. Permits are required, inspections are required, not doing either equates to big big big fines.
Dredging LH is a great idea - the problem is that the .gov that folks love so much make it near impossible to do. It literally takes years of red tape, environmental impact studies (not just on the lake impacts, mind you, but on the environment where dredge material will be deposited as well, and don't forget impact studies on haul routes, air quality and a few other things that all take time and money), feasibility studies, cost to benefit impact studies, lobbying for funding and the consumption of resources and time required for that aspect, cooperation from multiple federal and state agencies (each with an agenda, each with a limited budget and each with different stated capacities), bidding the work and then finally doing the work. And LH isn't exactly an easy body of water to simply dredge due to the fact that it is man made, is a source for drinking water (which means that dredge operations have to be done in a manner that will not negatively impact the ability to treat said water to potable standards with existing equipment or without damaging existing equipment). Not to mention the subsurface conditions - being that it is a man made reservoir, a significant portion of the lake bed is debris ridden with the vegetation and tree stumps that was there prior to the lake being constructed. So standard dredging equipment is not going to work and specialized equipment will need to be designed, fabricated, procured, demonstrated, etc.
As far as Dickinson not being subject to future flooding - yeah, no. You want to know the single biggest factor in any of the floods (obviously outside of significant weather events)? Development. Urban growth. Building in areas that should not be built in. Areas that are high and dry but channel 10x the amount of water that natural vegetative cover channels to the same rivers and bayou systems that we can't modify. The exponential population and subsequent development growth in the greater Houston area that has no real end in sight.
Aside from the fact that Harvey was just a whale of a storm, we are going to continue to see more and more smaller scale storms produce flooding in areas "that have never flooded before!" because of compounding impacts. A master planned development in a vacuum may not have any significant impact on drainage and flooding, but 15 of them in close proximity outside of a vacuum do. So it's not just Kingwood, it's every area that you look that has ongoing development. Which is a 360 degree swath around Houston.
Another major contributing factor is the fact that since about 1825, we have absolutely changed the natural ecosystem along the gulf coast. Not just through development, but through changes in plant life from native salt and switch grass prairie land to pastures covered in Jiggs and Coastal and Bermuda that simply do not handle the severe weather patterns the same. It is estimated that there is less than 1% of the native gulf prairie system still in existence - and the various prairies along the gulf coast were measured in millions of acres. We don't have natural wildfires that maintain vegetation lines. We levee and channel river systems and don't let them change course like they did for a million years before we came here. We don't allow rivers to flood annually like God's design and instead build houses right on the banks. We bring in new plants that aren't native here and change the surfacescape. All of these have impacts that might not be significant when measured individually, but when measured as a whole have a monster impact.
So yeah, I'll keep having fun with this thread. You may succeed in solving the problem that affected you, but the end result is that you will cause a problem for somebody else. Or 10 years from now the fix you lobbied for today will be rendered ineffective because of 10 years worth of developmental changes that were not accounted for when the problem was identified today.
That's not to say that policies and procedures should not be reviewed and modified where necessary - but you are among one of the ones on this thread that have maintained that there was some type of criminal and deliberate act perpetrated to get those rich Kingwood folk, so I'm a bit skeptical of your ability to grasp the entire picture. Even with your 200+ patents and PHD sitting on the wall.