var styles = {
    'lines': new ol.style.Style({
        stroke: new ol.style.Stroke({
            color: 'blue',
            width: 1.25
        })
    }),
    'labels': new ol.style.Style({
        text: new ol.style.Text({
            text: '',
            font: '15px sans-serif',
            fill: new ol.style.Fill({
                color: 'red'
            }),
            offsetY: -11,
            placement: 'line',
            maxAngle: 0.25,
            overflow: true
        })
    })
};

function style_rivers(feature, resolution) {
    var stylesArray = [];
    stylesArray.push(styles.lines);
    styles.labels.setGeometry(feature.getGeometry().simplify(0.9));
    styles.labels.getText().setText(feature.get('name'));
    stylesArray.push(styles.labels);
    return stylesArray;
}