Such roofs are pitched at slopes of 1 : 100 to 1 : 50 toward interior drains.
"We found this to be one of the biggest drawbacks to interior drains," Mr. Bevilacqua said.
Homeowners who would rather not dig an 18-inch trench around the inside wall of their basement can install a Waterguard interior drain system designed by Mr. Janesky.
Joseph Bevilacqua, president of B-Dry Waterproofing System, a national waterproofing franchise based in Akron, Ohio, said that even interior footing drains eventually clog with sediment and algae.
North of the central highlands, and parallel to them, a broad interior plain drained by the Lempa River is situated at elevations between 1,300 and 2,000 feet (400 and 610 metres).
Later, uplift exposed the Moenkopi Formation to erosion and Utah became part of a large interior basin drained by north and northwest-flowing rivers in the Upper Triassic.
Most of the city's interior is drained by the small Hyeongsan River, which flows north from Ulsan and meets the sea at Pohang Harbor.
Working with the cinematographer Adam Kimmel and the production designer Mark Digby, Mr. Romanek creates a plausible, coherent world, particularly at Hailsham, where the children's monochromatic uniforms and their muted affect are mirrored by interiors similarly drained of vibrancy.
Stream valleys have been deepened by glaciers to produce a fjordlike coast, with relatively short streams draining the interior.
In the interior, thawing permafrost is draining lakes and raising the risks of wildfire on bone dry forests.
Sediment carried by rivers draining the continental interior began to fill the basin from the north, a process that has continued to the present.
