Straw wattles are manmade tubes of compressed straw, also known as erosion logs. The compressed straw is held together with twine or wire. They are usually placed along the tow of newly disturbed soil on steep slopes and are meant to prevent soil from migrating off site. Alternate products would be hay bales and silt fences and the choice of one over the other might depend upon cost. The concept in all cases is to use these materials as fences to detain eroding soil on-site. They act as a barrier, but they do not prevent the slope from eroding, only to stop the soil from going off-site and they are meant to be temporary (but important) tools. They are usually removed after the soil has been stabilized with natural growth or ripwrap but they can be left in place to dissolve naturally. I can see their use along gravel roads to assist in retaining soil after heavy rains have damaged the road but not for any form of permanent erosion control. Of course, they could be used to channel soil laden water in a desired direction but still would only be temporary. I would also suggest using logs or hay bales that are held together with natural materials rather than plastic mesh materials that will not rot away. Consumer versions of this material can often be found in local hardware or big box stores while larger versions can be sourced from landscape or speciality suppliers.