I am not sure what is affecting your tree.  From the pictures it appeasr the tree is located either next to a driveway or road?  The Alaskan cedar has very few pests.  The most common include juniper scale, bagworms, beetle borers, spruce mites and spider mites. Diseases include tip, twig and needle blights, root rot, rust and phytophora. Blight is most common in young plants in nurseries or old plants in the landscape. Plants subjected to drought, freezing stress, mites or too much direct sun may also exhibit scorch. Scorch is a condition that appears as though the foliage has been burned.
Moderately drought tolerant, it grows best in high humidity in moist, slightly acidic to neutral soil
with excellent drainage. The ideal climate for weeping Alaskan cedar is mild summers followed by wet winters. Protect trees from southwest winds.
Additional information can be found at
https://plants.ces.ncsu.edu/plants/callitropsis-nootkatensis

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