There are peculiarities about the coastal plain in NC. It has no large river going to the Atlantic, unlike the Potomac and the James in Virginia, or the Santee and the Pee Dee in South Carolina, or the Savannah on the SC-Georgia border. The rivers that pass through the NC coastal plain — the Cape Fear, the Neuse, the Tar, the Roanoke, and the Chowan — are small in comparison. They don't have the natural capacity of rivers in adjacent states.
Furthermore there are few large lakes along these rivers in the NC coastal plain, whereas SC has situated numerous large lakes along its corresponding rivers in the coastal plain. Lakes serve an important role in flood control by buffering inflow while increasing outflow by a lesser amount over a longer period of time. North Carolina, in contrast, placed dams such as Falls and Jordan upstream in the Piedmont. That's understandable because the geography in the Piedmont is more amendable to deep lakes that don't require so much surface area and also because the populous Piedmont needed sources of drinking water. But the consequence is that Falls Lake and Jordan Lake are too far upstream to prevent the catastrophe that began Saturday.
The NC coastal plain is naturally vulnerable to broad floods, but this vulnerability has been intensified by the rapid population growth of the Triangle. Growth creates impervious surfaces such as roofs, parking lots, and roads. Although the Piedmont counties have attempted to mitigate this ever-increasing runoff with their own small-scale lakes — I live near one, Lake Lynn in north Raleigh — the attempt was only partly successful, in part because the growth of the Triangle has exceeded all estimates from the 1970s when these lakes were planned, in part because ongoing construction in the Triangle has silted up these lakes and reduced their capacity to hold temporary floodwaters.
And we have the sad story of the Woodlake Dam, built expressly to provide a scenic and recreational environment for a country club and resort development. The weakness of this dam has been known for some time, but there was no sense of urgency to fix it. The odds of a storm anytime soon that could overwhelm the dam seemed very low to officials.
What we saw Saturday was our own highly improbable but very real "perfect storm". The combination of Hurricane Matthew and a cold front moving rapidly from the northwest to the southeast produced far more rain than anyone expected. The National Weather Service has confirmed one reading of 18.38 inches in Elizabethtown (for my European friends, that's almost half a meter of rainfall). At my house I measured 10 inches. There was brief flooding in the Triangle, but the real problem began on Sunday and Monday as the bolus of rainfall departed the Piedmont rapidly and moved into the coastal plain that would have had difficulty expelling the rain it got itself, much less what came from upstream.
The catastrophe is upon us. Many have died. No, not as many as in Haiti, but deaths nevertheless. Property damage and economic disruption will be extensive. After similar floods in 1996 from Hurricane Fran and 1999 from Hurricane Floyd, the coastal plain took 10 years to recover. In some cities such as Rocky Mount, the recovery was never full. The coastal plain, in general, has not enjoyed the economic prosperity of the Piedmont or the beaches. Financial resources of coastal plain counties were already stretched thin before Saturday.
And what people in NC aren't keen to discuss is that the lowest elevations of inhabited land in the coastal plain are disproportionately occupied by African-Americans, Latinos, and Native Americans who cannot afford to live on higher land. Metro New Orleans saw this too in the aftermath of Hurricane Katrina. The poor will suffer not only a loss of life and property, but also a loss of livelihood because many businesses in the affected areas will close indefinitely. Yes, there will be jobs in construction but the poor often have no skills for those projects and the number of openings for unskilled labor will not nearly match the number of people looking for work. Meanwhile, our NC General Assembly has cut employment insurance benefits to the bone.
The perfect storm would have inflicted misery, for sure, but our own choices have multiplied that misery.