Taking further issue with those who see knowledge of plants as the central defining feature of landscape design, I like to emphasize the importance of surface water design. Granted, life on earth would be impossible without plants, but plant growth is not possible without fresh water. So water comes first. Those who live in arid countries know that water must be used as many times as possible before it returns from whence it came. Inhabitants of humid countries habitually squander their watery wealth. It would be no bad thing if the public came to think of landscape architects as people with expertise in the organization of landform and water.
When I was a student, the only aspect of surface water management that we learned was "drainage'. Those cultural theorists who now debate the place of rationality in public policy may be interested to learn that we were taught the Rational Method. It began with rainfall tables and indices of soil permeability (see Essay 10). This gave a measure of what quantity of water would have to be accommodated in drains at certain time intervals ("the five-year storm'). After that, all we had to do was size the drains and position the gulleys. This approach should now be renamed: the Irrational Method. Today, we aim to detain, infiltrate and evaporate rainwater before it ever gets near a drain. This approach is more sustainable. When designing outdoor space, please keep asking yourself "Is this paving really necessary?' If the answer is affirmative, ask the supplementary question: "Can the paving be porous?' In Paris, most of the footpaths in most of the parks are absorbent. In London, they are waterproof. The explanation, perhaps, lies with the French conception of rationality.
"All outdoor surfaces must be laid to falls.' The way to learn about falls is to look at every hard surface your eye lights upon and discover what happens to the rain that falls upon it. This is easiest in wet weather. It is a very interesting subject, but take care not to walk into lampposts when exercising your new hobby.
Floods can be beautiful
