The scope of the devastation is staggering. Houston is the fourth largest city in the nation, bigger than the state of New Jersey with a population of more than 2.3 million within city limits and 6.5 million throughout the metro area. Across the state, Hurricane Harvey affected more than 6.8 million people in 18 counties. As the days pass, the damage and death totals continue to rise. So, too, do the number of volunteers.