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I know this question has arisen before, but my search only returned results of arguments between the merits of the 17-40L vs the 16-35L. Simply put: Is the Canon 17-40L a worthy landscape lens if it's exclusively used for landscapes?
If you shoot full frame and your preference is for (what might be regarded as typical) small aperture shooting from the tripod, the 17-40 is as good as any other Canon zoom that covers this focal length range. It can produce excellent image quality suitable for making very large prints.
For this sort of work, the 16-35 f/2.8 has little or no advantage. It is a fine lens, but its strength is primarily as a larger aperture ultra-wide for low-light hand-held shooting on full frame cameras, where its extra stop and better performance at the very largest apertures is useful. But when you stop down to the apertures you are likely to use for landscape, it produces no better image quality than the 17-40. It is larger, heavier, and considerably more expensive, and it requires the larger, more expensive, and arguably non-standard 82mm filters. (If you need this lens for other types of photography that you do, go ahead and use it for landscape - it will work well. Just don't rush out get it for this purpose based on the assumption that it will produce better photograph quality because it is bigger, badder-looking, and more expensive.)
If you shoot a cropped sensor camera, I recommend against either of these lenses for landscape photography. For covering this focal length range your best bet is almost certainly the EFS 17-55mm f/2.8 IS lens. The image quality actually tests better in some ways - especially corner performance - than the two L lenses when used on crop sensor bodies, it also gives you the f/2.8 maximum aperture, it provides image stabilization (useful in those case when you might hand hold, and not available on either L lens), and it has a larger focal length range.
Some will urge you to shoot primes or even tilt/shift lenses. There is no question that you can do this, but you need to think this through very carefully.
As to regular primes, while they can produce "better" image quality at the largest apertures, at the smaller apertures typical of much landscape work the difference declines to the point where it is often insignificant. And some of the best zooms produce truly excellent image quality that differs in no significant way from that of very good primes. (I shoot both, by the way.) And unless you are shooting from the tripod, using MLU or live view and a remote release, and regularly pushing the upper boundaries of very large print size, the differences in image quality will be quite invisible. There is also the issue of flexibility of primes versus zooms. Not all landscape photography is done at a pace or in circumstances in which you have the luxury of carrying large numbers of lenses, taking lots of time to switch among them, or in which you have so much freedom to move change your camera position that you can afford to limit your focal length options. In compositional terms, you are much more limited with primes since the control over composition afforded by focal length variation is much more limited with only a few primes. This can play out in surprising ways in regards to image quality. Let's say you have a 24mm and a 35mm prime, but the ideal composition works out to be at 32mm. You could choose a less-than-ideal composition with the 35mm lens or you could shoot the 24mm and crop in post. However, with the zoom you could "crop in camera" and retain the full original image quality. Here, any image quality difference between prime and zoom will diminish or even reverse!
Tilt/shift lenses are a whole other issue. Frankly, the number of people actually using them in the field, especially among what you might call "serious" landscape photographers is very limited. I'm fortunate enough to "hang with" a good number of such folks, including some who cut their photographic teeth on large format film photography... and I don't know a single one who regularly goes into the field with a TS lens. One or two might occasionally use one for a very special shot, but most don't. While there are those in photography forums who will act as if serious landscape photography requires TS lenses - and there is a very small number of good photographers who actually use them at times - their use in the real world is far, far less than the discussions among equipment geeks might suggest. Go slow on that one!
I don't know who your landscape photography heroes might be, but several successful and well-known landscape photographers who shoot Canon and do very good work rely on the 17-40.