Wouldn't it be easier or better to straighten the stream and rip-rap the stream banks than leave it in its meandering form?

No, this is one of the major sources of our present flooding problems.

Channelizaton of streams has helped to produce the flashy runoff and flooding problems that face many parts of the country. It is estimated that nearly one half of the original stream miles in Iowa have been lost because of channelization. When a stream is channelized it is significantly shortened, which reduces channel storage capacity and increases velocity. When high flow events do occur water is accelerated because it moves through a straight channel and no longer is slowed by hitting meandering banks. Higher velocities also mean higher erosive potential which tends to downcut the channel. This reduces the ability of the channel to use its floodplain to slow the flow of water. Because the channel has been shortened, the same amount of water now flows in a shorter reach without access to its floodplain, resulting in high velocity water being delivered rapidly downstream producing potentially severe floods.

Using rip-rap on banks hardens the banks and often makes them smoother than when plant stems and roots provided a frictional surface. Unless properly applied rip-rap also may be undermined and collapse into the channel as often happens when broken portions of road construction debris are dumped along a bank. Rip-rap is significantly more expensive than bioengineering and is also aesthetically less pleasing. A combination of bioengineering using living woody plants and grasses along with properly applied hard-engineering, such as rip-rap is often the best solution to bank stabilization.