Dec 1 (Reuters) - Houston, Texas-based Kirby Inland Marine (KEX.N) agreed to pay $15.3 million in damages and assessment costs to resolve federal and state claims for harm to natural resources resulting from a 2014 oil spill from a Kirby barge in the Houston Ship Channel, the U.S. Justice Department said. In a related enforcement action in 2016, the United States secured a settlement with Kirby for $4.9 million in civil penalties and injunctive relief measures to improve the company"s operations to help prevent future spills. The United States and Texas concurrently filed a civil complaint along with a proposed consent decree. The complaint sought money damages and costs under the Oil Pollution Act for injuries to natural resources resulting from Kirby"s March 2014 discharge of about 4,000 barrels (168,000 gallons) of oil from one of its barges into the Houston Ship Channel, the department said in a statement on Wednesday. The complaint alleged the spill resulted from a collision that occurred while a Kirby towboat attempted to push two 300-foot-long oil barges across the Houston Ship Channel in front of an oncoming 585-foot-long deep-draft bulk cargo ship that was already under way in the Channel. The oil flowed from the Houston Ship Channel into Galveston Bay and the Gulf of Mexico, polluting waters and washing onshore from the collision site down to Padre Island National Seashore near Corpus Christi. The oil spill caused significant harm to the Texas coastline including the wildlife refuge on Matagorda Island, and to aquatic and terrestrial habitats, as well as to dolphins and migratory birds, the Justice Department said. The oil spill also forced the closure of the Houston Ship Channel and disrupted recreational uses of the Texas coastline. "This case illustrates that the stakes are high, the harms are serious", said Assistant Attorney General Todd Kim for the Justice Department"s Environment and Natural Resources Division.