Cal. Gov't Code § 66478.4

(a) No local agency shall approve either a tentative or a final map of any proposed subdivision to be fronted upon a public waterway, river, or stream which does not provide, or have available, reasonable public access by fee or easement from a public highway to that portion of the bank of the river or stream bordering or lying within the proposed subdivision.
(b) Reasonable public access shall be determined by the local agency in which the proposed subdivision is to be located. In making the determination of what shall be reasonable access, the local agency shall consider all of the following:
1. (1) That access may be by highway, foot trail, bike trail, horse trail, or any other means of travel.
2. (2) The size of the subdivision.
3. (3) The type of riverbank and the various appropriate recreational, educational, and scientific uses, including, but not limited to, swimming, diving, boating, fishing, water skiing, scientific collection, and teaching.
4. (4) The likelihood of trespass on private property and reasonable means of avoiding these trespasses.
(c) A public waterway, river, or stream for the purposes of Sections 66477.2, 66478.4, 66478.5 and 66478.6 means those waterways, rivers and streams defined in Sections 100 through 106 of the Harbors and Navigation Code, any stream declared to be a public highway for fishing pursuant to Sections 25660 through 25662 of the Government Code, the rivers listed in Section 1505 of the Fish and Game Code as spawning areas, all waterways, rivers and streams downstream from any state or federal salmon or steelhead fish hatcheries.