How to do side filling of an image

We need to detect the ground using simple filling starting from the bottom of the image shown below. Any suggestions?

This codes what i have done so far,

rgb=imread('obstacle_scene_1.jpg'); 
figure, imshow(rgb);
rgbImage = imread('obstacle_scene_1.jpg');
hsvInt = rgb2hsv(rgbImage);
hsvDouble = rgb2hsv(double(rgbImage));
figure, imshow(hsvInt);
figure, imshow(hsvDouble);
level = graythresh(hsvInt);
bw = im2bw(hsvInt,level);
bw = bwareaopen(bw, 50);
figure, imshow(bw)

what i want is

Answer 1

[Image Analyst]

Perhaps this:

bw = imfill(bw, 'holes');