Why is Meryl Streep, a two-time Oscar winner best known for her dramatic roles, starring in a big-budget action flick? Well, for one thing, she felt it was about time that audiences discovered that a daredevil lurks somewhere beneath her serious, Vassar-educated facade. “I wanted to stretch myself physically,” she says. “I’m not someone who works out normally and I wanted to test myself. And it had to do with having children and reaching a certain age where I stopped doing crazy things. I became the person who would say, `Watch out. Don’t do that. Don’t walk too close to the road. Don’t let her put that in her mouth. Come down. Now!’

“I look at my kids and they’re so reckless and fearless. I wanted to get back to that feeling of being a little too high in the tree. You know, that feeling when you go out on the ice before it’s really frozen, before anybody else’s skates have crossed it? I used to be like that. I wanted to rediscover that feeling.” Streep, 45, shows off her physical prowess – not to mention her newly buffed bod -in Curtis Hanson’s “The River Wild,” the best movie about a river-journey-gone-sour since “Deliverance.” The film opens today in area theaters. “Whatever else the movie is, I kiss Curtis Hanson’s feet that he let me be paid to be in Montana for four months,” says Streep. “It was beautiful.”

Before accepting the role of an accomplished oarswoman who is menaced by a duo of thugs (Kevin Bacon and John C. Reilly), Streep received assurances from Hanson (“The Hand That Rocks the Cradle”) that he’d allow her to help create her character. “I didn’t want to be a figure in the landscape,” Streep explains. “I met with Curtis and he said he didn’t know who these people (in the script) were yet. But he was willing to shape it with my collaboration. With that understanding, I thought, `This could be really cool’ … I see the movie now and some scenes are mine. The giggling scene is mine. We had this boring plot thing to achieve. I wanted to undermine the bad guys and their macho posturing. I wrote that scene 15 minutes before we shot it.”

The film, which crests with a battle of wits between Streep and Bacon, is proof that the actress is determined to peel away the Mistress of a Thousand Accents label that has stuck to her since the days of “Sophie’s Choice,” “Out of Africa” and “The French Lieutenant’s Woman.” “A lot of other people do accents and nobody mentions it,” Streep notes tersely. “You know, if I only played dishwater-blondes from New Jersey I would have a really limited career. When I was younger and less well-known, I think it was easier for people to think of me as Sophie (in `Sophie’s Choice.’) Now, it’s different.” In the past, Streep has tried to re-invent herself as a comic actress. But lightweight fare such as “Heartburn,” “She-Devil,” “Defending Your Life” and “Death Becomes Her” pleased neither her fans nor critics.

“When I started out in drama school, I was known for doing comedies,” says the Summit, N.J., native. “People in my class were shocked that I had a career that was more dramatic … But whatever that first image of yourself is that you present to the public, it’s hard to overcome.” Does Streep think “The River Wild” will finally redefine her image in a way that her five comedies did not? “I don’t care what people think anymore,” she says. “I take the scripts that tickle me in some way. I work completely selfishly. I do things that I think will amuse my family and my friends. I’ve made enough money. I don’t care.” Streep insists that comments from writers such as Pauline Kael and Liz Smith mean nothing to her. “Liz Smith wrote that I was jump-starting my career (with `The River Wild’). Now everybody says to me, `You’re jump-starting your career.’ Once something is written by Liz Smith, it’s canon. I’ve never thought that way. I wouldn’t have done `A Cry in the Dark’ or `Ironweed’ if I thought that way. Those are weird movies.

“I wouldn’t have done them if I gave a s– about my image in Hollywood or what the grosses are going to be. I don’t even know who runs the studios. And I consciously don’t know. It makes me uncomfortable and diverts me from what I’m doing. It makes me think about things that I don’t want to think about.” Industry insiders believe positive advance word on “The River Wild” convinced Warner Bros. and Clint Eastwood to cast Streep in “The Bridges of Madison County,” the upcoming romantic drama based on the hugely popular Robert James Waller novel. “Somebody quoted me as saying that I hated the book,” says Streep, “so now I have to chase that rumor. What I said was that my soul wasn’t shattered by the book. Some people regarded it as a religious experience and traveled to Winterset, Iowa. I didn’t have that reaction. I wasn’t even interested in pursuing the part because the book didn’t affect me.” So, what changed her mind?

“My friend Carrie Fisher gave Clint my home phone number,” says Streep. “Then it became a courtesy thing. He called me and said, `I hear you didn’t like the book.’ And I said, `No, no, it’s not that. It’s just that I wasn’t destroyed by it like everyone else.’ He said, `Read the script. It’s good.’ The force of his voice over the phone made me say, `OK, OK, Clint, I’ll bet it is good.’ He sent it to me the next day. And it was wonderful.” How does the Ron Bass/Richard LaGravenese script improve upon the Waller original, which tells the Iowa-set story of an Italian housewife who has a brief but memorable fling with a lonely photographer? “Well,” says Streep, “(the screenplay) doesn’t describe everything like the book does. The book drove me crazy because he explained how they looked when they were feeling what they were feeling. All you get in the script is what they’re saying to each other. I can make up how they’re feeling in my head. I like that. I fantasize a lot.” Streep’s dedication to her craft is the stuff of Hollywood legend. She gained weight to play Lindy Chamberlain in “A Cry in the Dark” and razed her hair to play a concentration camp survivor in “Sophie’s Choice.” When she was shooting her death scene in “Ironweed,” she clutched a bag of ice to simulate the coldness of a corpse. She did this take after take, until, according to one witness, she willed herself into “a coma-like state.”

For “The River Wild,” she became a crackerjack river rafter. In fact, Streep became so accomplished at the sport that she wound up doing many of her own stunts, including performing runs down dangerous Class IV and V rapids. “When I finished the movie I didn’t want to even hear the water running in any part of my house,” says Streep. “But three weeks ago, I went down a river in Massachusetts with my kids and Tracey Ullman and her kids. We had a great time. But you certainly can’t impress Tracey. She just makes fun of you no matter what you do.” Since finishing “The River Wild,” Streep has moved from Los Angeles back to her home in Connecticut, where she lives with sculptor-husband Don Gummer and their four children, ages 3 to 14. “I didn’t really regard myself as living in L.A.,” she says of her three-year stint in Hollywood. “I made four movies there. But we always knew we’d go back to Connecticut.”