Columbia
Columbia Geography & Climate
Geography
Columbia stands at the point where the Broad and Saluda rivers join to form the Congaree, in the centre of South Carolina.
The fall line
The city sits on the fall line, the boundary where the hard crystalline rock of the Piedmont Plateau gives way to the soft sediments of the Atlantic coastal plain. Rivers drop over that edge in rapids and shoals, which historically stopped boats and provided water power — and that combination is why a line of southern cities, Columbia among them, sits along it. Upstream the country is rolling and red-clayed; downstream it is flat, sandy and swampy.
Three rivers
The Broad comes down from the Piedmont Plateau, the Saluda arrives cold from the bottom of a reservoir, and they meet downtown to form the Congaree. Because the Saluda is released from deep water it stays cold all summer, which produces river fog where the two meet and supports trout in a place that has no business having them.
Congaree floodplain
Downstream the river spreads across a broad floodplain that floods roughly ten times a year, bringing nutrients that grow exceptionally tall trees — the national park protects the largest remaining tract of old-growth bottomland hardwood in the country.
Sandhills
North-east of the city, relict dunes from an ancient shoreline carry dry pine and scrub oak.
Why here
The fall line gave the site water power and a head of navigation, and the legislature wanted a capital equidistant from the coast and the mountains. A canal was cut around the shoals in the 1820s to get boats past them, and its remains run beside the river as part of the greenway.
Lakes
Reservoirs on both rivers supply power, water and recreation.
Climate patterns
Columbia is one of the hottest cities in the United States in summer, and it is inland enough to have no relief from it.
Summer
June to September is long, hot and very humid. Highs average 33 to 34°C in July, days above 38°C occur most years, and the heat index regularly exceeds 40°C. Nights stay above 22°C. The city sits in a basin on the fall line, well away from the coast, with no sea breeze and no elevation, and the local nickname acknowledges it. Afternoon thunderstorms are frequent and brief.
Winter
December to February is mild: highs of 14 to 16°C and lows just above freezing. Hard freezes happen but do not last, and snow is rare enough that a few centimetres closes schools and roads. Ice storms are the more serious winter hazard.
Spring and autumn
Both are excellent and both are short. Spring comes early, with azaleas and dogwood in March, and autumn stays warm into November.
Rainfall
Around 1,200 millimetres a year, fairly evenly spread, with a summer maximum from thunderstorms.
Living with the heat
Deep porches, high ceilings, shade trees along the wide streets and a working day that starts early are all local adaptations, and air conditioning is what made the modern city possible. Visitors should plan the way residents do: outdoors early and late, indoors from midday.
Hurricanes and flooding
The city is far enough inland to avoid direct hurricane strikes but receives their rain; in October 2015 a stalled system dropped extraordinary totals and caused catastrophic flooding, breaching dozens of dams.