The floodgate has been opened already, but the fact that it turns September today will only increase the frequency and intensity of all the upcoming 9/11 tributes and films.

Two are on tonight. The second half of the two-part, six-hour look at what’s going up where the World Trade Center towers plays tonight – “Rising: Rebuilding Ground Zero” (Discovery, 8, p.m.) looks at some of the people involved in the ambitious, long-delayed project.

On  “Nick News: What Happened? The Story of September 11, 2001” (Nickelodeon, 9 p.m.), Linder Ellerbee attempts to set the record straight for kids who might have been too young (or nonexistent) when the planes hit. She sets to rest some rumors, and she sets out the terrible tale in remarkably simple and straight-forward language. But she also uses the comments of those, such as former Bush White House spokesman Ari Fleischer, who explains why Iraq was targeted, without anyone suggesting there might have been another position.

Elsewhere, “Inside 9/11” (National Geographic Channel, 8 p.m.) is paired with “Inside 9/11: The War Continues” (National Geographic, 10 p.m.).

This month is also a an anniversary of a terrible incident abroad – the Chechen kidnapping of 1,200 people in 2006 during “Three Days in September” (Showtime 2, 9 p.m.).

Rachel and Jordan were on the block for eviction on “Big Brother “ (CBS, midnight) — for about a minute. Then some convoluted rule fro the Pndora’s Box allowed both to stay. And now Porsche had to nominate two others for eviction. She turned against the newbies by choosing Shelly and Adam. One gets booted tonight.

Christine Baranski lends her voice to the second season finale of “Ugly Americans” (Comedy Central, 10:30 p.m.).

Last chance to catch the best 15-minute satire on TV, “Children’s Hospital” (Cartoon Network, midnight).

Turner Classic Movies host Robert Osborne is taking the month off, letting others will in as between movie hosts. First up is Illeana Douglas. Tonight, she presides over a 50th anniversary celebration of Ismail Merchant and James Ivory with a line of their classy, well-detiled work over the years, from “The Householder” (8 p.m.) to “The Creation of Woman” (9:45 p.m.), “Shakespeare-Wallah” (10 p.m.), “Bombay Talkie” (12:15 a.m.), “Helen, Queen of the Nautch Girls” (2:15 a.m.), “The Delhi Way” (3 a.m.) and “The River” (4 a.m.).

The U.S. Open (ESPN2, 1 and 7 p.m.) continues in Flushing Meadow.

The college football season starts with UNLV at Wisconsin (ESPN, 8 p.m.).

Daytime Talk

Regis and Kelly: at Prince Edward Island. The View: Cat Cora, Ming Tsai, Marcus Samuelsson, James Woods, Jessie J, Tyra Banks (rerun). The Talk: Barry Manilow, Suzanne Somers (rerun). Ellen DeGeneres: Halle Berry, Josh Groban (rerun). Wendy Williams: Kelsey Grammer (rerun).

Late Talk

David Letterman: Julianna Margulies, Joe Wong, Lady Antebellum. Jay Leno: Heidi Klum, Kevin Smith, Fitz and the Tantrums. Jimmy Kimmel: Jamie Foxx, Affion Crocket, the Vaccines. Jimmy Fallon: Ann Curry, Wayde King & Brett Raymer, Lenny Kravitz. Craig Ferguson: Kathy Griffin, Lynette Rice. Tavis Smiley: Randall Kennedy. Carson Daly: Anthony Ameen, Sarah Vowell, Goldheart Assembly (rerun). Jon Stewart: Mark Adams (rerun). Stephen Colbert: STS-135 astronauts (rerun). Conan O’Brien: Zach Galifianakis, Sig Hansen, Raphael Saadiq (rerun) . Chelsea Handler: Lake Bell, Brad Wollack, Greg Fizsimmons, Heather McDonald.