Just before the boy says "Dad, we can do this..." a blue car is driving on the road behind Evan. In another angle, as Evan sits down, the car has disappeared. In the shot of the children after Evan says "we need something to lift those beams" the car appears again on the left side of screen. (widescreen version only)
The European map on the wall in the hallway is totally incorrect. Portugal seems to be part of Spain, Turkey is smaller, there's a new country on eastern Mediterranean and Northern African countries are dislocated.
In the movie's opening scene, Evan Baxter anchors one more newscast before leaving for his new job as a U.S. Congressman. In reality, this would create a conflict of interest. By Federal law, Baxter would have to resign as a news anchor prior to launching his campaign, or the TV station would have to provide free equal time to his opponents.
When Evan is in his office surrounded by birds, behind him are two blue peacocks. Within the story we are meant to believe that this is a breeding pair, but they are both male. Female peacocks (peahens) are brown.
A freshman member of Congress would not move his family to the Washington area, and would not purchase a large house. Congressman are required to maintain residency within the state in which they were elected. A freshman Congressman would likely rent a small apartment, or (like Representative Jason Chaffetz) sleep in his office.
The area code for the phone number on Eve Adams's real estate signs is 804, which is the area code for Richmond, some two hours away from Washington, D.C. Northern Virginia's area code is actually 703.
The water level in the lake is shown as level with the top of the dam (full). If the D.C. area had really lain under an exceptional drought all summer, as stated, the water level should have been much lower.
At the beginning of the film, when Evan is praying at the end of his bed, there is a light shining from the left side of the screen. There is also a light shining through a window behind him when the shot changes. Assuming this scene takes place at night, the light makes it clear that this scene was shot during the day.
When the storm surge dumps the Ark into the Potomac river, Rosslyn (a portion of Arlington) is visible in front of them. Rosslyn is on the other side of the river so it would have not been visible. Also, as they approach Memorial Bridge, they show Georgetown to the West of the Ark. Georgetown is on the east bank of the Potomac, and the river makes a big bend south at that point. We should have seen Arlington and Arlington Cemetery at that time.