Trucking fleets, railroads and shipping lines are rerouting cargo and setting up alternate supply lines as\u00a0Tropical Storm Harvey promises to disrupt\u00a0freight traffic across southeast Texas for days.<\/p>\n

Seaports in Houston and Corpus Christi\u00a0have been closed to most ships\u00a0since before Harvey made landfall Friday, and rising waters from\u00a0days of heavy rains and catastrophic flooding\u00a0are threatening long stretches of highways and railroad tracks, bringing freight transportation in a major American hub to a virtual standstill.<\/p>\n

The number of Houston-area trucking runs requested plunged 80% Sunday, according to the most recent data from DAT Solutions, an online load board.\u00a0Union Pacific\u00a0Corp.<\/span>UNP\u00a0+0.18%<\/span>\u00a0has halted all freight rail traffic bound for Houston and surrounding areas, while\u00a0United Parcel Service\u00a0Inc.<\/span>\u00a0UPS\u00a0+0.63%<\/span>\u00a0has suspended freight service in Houston and Beaumont, Texas, and is offering limited service as far west as San Antonio. Two Maersk Line container ships remain anchored in the Gulf of Mexico, joining oil tankers and\u00a0cruise ships waiting for Houston\u2019s port to reopen.<\/p>\n

The gridlock will likely reverberate beyond Texas, threatening to snarl international trade routes. Houston is a key consolidation point for imports of vehicles and appliances made in Mexico, and stores as far away as Denver bring in foreign-made goods via the city\u2019s port.<\/p>\n

The storm affected up to 10% of the U.S.\u2019s trucking capacity, according to No\u00ebl Perry, chief economist with Truckstop.com, another online load board. Retailers and other shippers around the country may struggle to line up enough trucks to ship goods. And many trucks that are available are being turned over to relief and rebuilding efforts.\u00a0Wal-Mart StoresInc.<\/span>\u00a0has sent more than 1,000 big rigs to hard-hit areas and evacuation centers, with most carrying water.<\/p>\n

Shipping costs could rise anywhere from 5% to 22%, Mr. Perry said, based on the market\u2019s response to past natural disasters, including Hurricane Katrina and the \u201cpolar vortex\u201d that hit the Northeast in 2014.<\/p>\n

Many freight companies say they have no idea when they will resume operations. Even after the weather clears, it could be days before floodwaters recede enough to allow dockworkers back into ports, or trucks to resume routes.<\/p>\n

\u201cThis may be unprecedented when all is said and done,\u201d said Mark Rourke, chief operating officer at\u00a0Schneider National\u00a0Inc.,<\/span>\u00a0a large Green Bay, a Wis.-based trucking company. He said it could be three days before Schneider employees can access some terminals in the city and potentially two weeks before normal operations resume.<\/p>\n

Darren Hawkins, president of Overland Park, Kan.-based YRC Freight, said the trucking company\u2019s terminal in Houston has remained closed since Friday when workers were sent home, and the company hasn\u2019t decided when it will be able to reopen.<\/p>\n

\u201cWe have about 3 feet of standing water in the parking lot,\u201d he said.<\/p>\n

YRC has been holding freight bound for Texas near the origin point since the middle of last week, adding trailers to keep goods at sites throughout its nationwide network.<\/p>\n

Mr. Hawkins said YRC was bringing some critical shipments needed for relief, including generators and bottled water, to staging areas authorities have set up around Houston. But it could be some time before operations get back to normal, he said.<\/p>\n

\u201cBy the time the city is open again, there is going to be a tremendous amount of tonnage going in,\u201d Mr. Hawkins said. \u201cThis is looking like a multi-day event, and so it\u2019s not over, and means the recovery will be that much longer. With Katrina, we had almost immediate access [after the storm surge] to the area. That\u2019s not the case with Houston.\u201d<\/p>\n