Property regulation with streams is very complicated. Many small creek and streams flowing through private property can not be accessed as there is no such thing as high water mark and the owners do own the river property but just the the right to it's contents which belongs to the crown. Usually high water mark only applies to rivers with flood control (dykes), as this is maintained by public funding and is usually built on crown land. However, if flood did occur and dykes are pushed back and onto private property well, it becomes a sticky situation. Dyke itself is owned by crown but not the land it's sitting on. So property owners does have the right to ask people to leave until crown buy the land from the owners. But on the other hand dyke is public access, so usually if all parties play nice, be neat and considerate, we won't have problems. So just remember some dykes are on private land and that's the backyard for some people. So don't just walk on top of the dyke, instead walk the dyke close to the water and not be seen, and be very quite.