Introduction

This method appears to date back to permaculture in the 1970's, and consists of two features that complement one another. 

These can work separately or in conjunction to slow water and redirect it through landscape where it can reduce local temperatures and heat island effects, reduce pollution and erosion, all while reducing the chance and impact of flooding down stream. When water is slowed down and moved strategically across a property, that water feeds the soil slowly which sequesters water where roots can reach it, which reduces water needed for gardens and crops. Over time, these structures can also help water recharge ground water resources. 

Swales

Swales are fairly shallow channels dug into the ground to capture and redirect rainwater, while berms are raised sections of ground which can be created using the excavated soil from the swales. By slowing water flow, swales not only prevent immediate run off and downhill flooding, but that extra time spent in one place allows that same water to instead begin seeping down into the ground and surrounding areas such as nearby flowerbeds. 

Swales can be particularly useful in places experiencing droughts, heavy but less-frequent precipitation, and places where aquifers are unable to replenish quickly enough to overcome local ground water extraction.

Berms

Berms help prevent overflow from the swales both by blocking water flow that would otherwise become run off. In other words berms help reduce flooding, as well as run off which can contribute to soil loss and water pollution.

It is recommended that you incorporate biological materials into your berm, particularly if you are working with poor soil. For example if the soil excavated from the swales is heavy in sand or other materials that don't absorbe water, then you may want to start the berm off with materials such as wood (sticks or logs that are lying around the area), compost, or even leaves (check first to make sure the type of leaves don't act as natural herbicide such as pine needles or pecan or black walnut leaves), then  add the excavated soil on top. You can actively mix the more nutritious elements as you go, create layers, or simply create a nutritious core with the less-nutritious soil added over the top and sides. Once finished with the basic shape, compost can help prevent erosion from rain or wind in the short term, but planting grasses or other plants directly into the berm will provide further stability as the roots weaver their way through the soil, and the foliage above will further prevent erosion. 

Bioretention

In addition to preventing erosion via basic physics, plants that grow along a berm, help water permeate deeper into the soil and absorbe still more water for growth and expiration in the atmosphere.