Select dropdown not going to option url
What you're currently seeing is the correct URL for a GET form submission.

You'll need to update the onsubmit handler to construct the URL you wish to visit, based on the selected option.

Here's how to do that, using the omnipresent jQuery. You could probably do the same in plain JS, but I have no idea which browsers you're targeting:

(function ($) {
    $('#sitemap').on('change', function (event) {
        var $select = $(this);
        var $form = $select.closest('form');
        var url = '/desired/path/to/development' + $select.val();

        window.location.href = url;
    });
}(jQuery));


Don't forget to remove the current handler from the markup.