I guess you've never worked with dirt before. In short: rain washes dirt away.
That being said, I went to a place last weekend where they coated the lips with asphalt. Hadn't been there for about 6 years, and the lips haven't changed at all!
I don't think he was suggesting you never need to maintain a well built track or at least I hope not. But if a track is built right the first time in a way to withstand wet weather the tracks are ok to ride in the wet and the maintenance is no more than a dry track we have now. Perfect example is the UK, there tracks need to be built to withstand wet weather and they do this, this means they can ride in the wet and can ride with its shitty weather. It keeps maintenance and damage to a minimum. No doubt we will always need to maintain a track but a well built track can make a big difference.
I am a advocate of riding in the wet and you only need to read a thread I started a while ago to know that many don't have the same view (it is a different thread to the one mentioned earlier) but wet riding is great fun and has some good skill developments, but you do need to be mindful of what you are riding, I am lucky enough to have some well built private tracks that stand up to the weather well so if its wet I go for it, but I still try to fill in any ruts after my session.
Here in AUS we don't build weather sustaining tracks as often and i would put this down to a few things;
1.Time - it takes slightly more time to get this done and resources might need to be gathered from other places than just the dirt in the bush.
2.Cost - while cost would not be significant it would be more that a traditional track.
3.Practicality - Although a wet weather built track is helpful when we ride it in the dry it does not prevent damage anymore than a non weather built track so somewhere like AUS were we tend to have more dry days than wet I guess it is not thought as a major need.
While there are some significant things you can do for wet weather tracks even following a basic trail building guide will give a trail fairly good weather resistance.
Roots - one of probably the most common problems with trail builders, do NOT remove roots or tree stumps unless absolutely necessary, roots help hold the trail together and keep dirt where it should be, likewise tree stumps do the same and help prevent dirt running or falling away.
Rocks - rocks again same principal as roots, we need them, also rocks clearly don't absorb or get softer with water, they wont wear down from riding on them wet so they are great for keeping the track together to hold soil etc but also provides a good surface that doesn't degrade or rut in the wet.
Gradient - as a general rule try not to or don't exceed half of the slope so for every meter you go down go across 2 meters.
Yes there will be corners down or sections that run down but try keep them minimal or for track direction change to cut back across.
Drainage - plan out the drainage before hand, drainage will keep puddles away it will not only keep water off the track therefore making it less wet but it can direct water away from the track to prevent rutting from water flowing.
Wet checking - check the planed track when it is raining, this will show you where the water naturally pools or runs and can help you plan drainage properly and direct your track around the potential issues.
These should be done for a dry track but have clear benefits for when it rains, the track will dry out faster, be less wet in the first place, hopefully less dirt will be moved away from the track and it should stand up to not only abuse but weather better.
