Append parameter to url
$('#wenmbm-banner-type-dropdown').on('change', function(){
var bannerType = $(this).val();
var url = window.location.pathname;
if (url.indexOf('?') > -1){
url += '&banner-type='+bannerType
}else{
url += '?banner-type='+bannerType
}
window.location.href = url;
//alert(bannerType);
});