We first established where we were in relationship to the bridge and grounded the left and right sides of the composition. Seated on the left meant that we were seeing more of the left side of the bridge than the right. We took a measure of the distance between the tree on the left and the first bridge support and compared it to the distance between the two bridge supports. Our instinct was to put the canal in the center of the page and carry it up past the horizon line. We countered this by noticing that it vanished below the horizon line and followed a diagonal closer to horizontal than vertical.
In my first pass I sought to define the predominant light and shadow shapes as well as some of the colors that caught my eye.
For the second pass I focused on conveying the overall green of our subject and re-stating the shadows.