The Texas county where nearly 100 people were killed and more than 160 remain missing had the technology to turn every cellphone in the river valley into a blaring alarm, but local officials did not do so before or during the early-morning hours of July 4 as river levels rose to record heights,

The geography of Texas makes it one of the deadliest places in the US for flooding. Texas Hill Country is made up of shallow rivers which run through rugged valleys, winding around hills and steep terrain.