Preheat oven to 350 degrees F. Spray a 13x9 glass baking dish.
In a mixing bowl, combine canned pumpkin, water, eggs, maple extract, and pumpkin pie spice until well blended.
In a separate bowl, combine cake mix (press out any lumps) baking soda and ground flax. Fold into pumpkin mixture just until blended. Pour into prepared dish.
Topping: In a separate bowl, blend brown sugar, flour, and melted butter. Sprinkle evenly over top of the cake. Spread nuts over topping.
Bake in preheated oven for 30-35 minutes or until a toothpick comes out clean.
Glaze: In a saucepan, combine brown sugar, sugar, maple extract, liquid creamer and bring to a simmer. Remove from heat and stir until sugar is dissolved. Immediately pour over baked cake. If you'd like, poke a few holes in the cake before pouring glaze over.