@Override
    protected Transferable createTransferable(JComponent c) {
        Transferable t = null;
        if (c instanceof JList) {
            @SuppressWarnings("unchecked")
			JList<River> list = (JList<River>) c;
            Object value = list.getSelectedValue();
            if (value instanceof RiverComponent) {
                t = (Transferable) value;
            }
        }
        return t;
    }