The technical term for a speed river?

There isn't a single technical term for a "speed river." The term itself isn't a technical one, but rather a descriptive phrase.

Here are some terms you might use to describe a fast-flowing river, depending on the specific characteristics:

* Rapids: A section of river with a steep gradient and fast-flowing water, often with large rocks or other obstacles.

* Torrent: A rapid and violent stream of water.

* Whitewater: Rapid water with turbulent flow, often seen in rivers with steep gradients and/or rocky sections.

* Braided river: A river with multiple channels that split and rejoin, often indicative of a high flow rate and sediment load.

* High-gradient river: A river with a steep incline, leading to faster flow rates.

* Ephemeral river: A river that only flows during certain times of the year, often associated with periods of high rainfall.

The best term to use will depend on the specific characteristics of the river you are describing.