Mix brown sugar, oats, flour and cinnamon in small bowl. Add butter and water, rub between fingers until evenly moistened. Stir in pecans; press together to form small clumps.
Heat oven to 350°F Line a 9 x 13 baking pan with nonstick foil. Let ends of foil extend about 2 inches above pan on short sides.
Beat sugar, butter, spices, vanilla, baking soda, and salt in large bowl with mixer 3 minutes until blended. Beat in eggs, one at a time, beating well after each. Alternately beat in flours with sour cream on slow speed until just blended.
Spread batter evenly in pan, sprinkle with streusel and bake for 35 minutes or until a toothpick inserted in center comes out clean. Cool completely in pan on wire rack. Lift cake by foil ends onto cutting board and cut into 24 squares.