I suppose they didn't feel a stile, gate, or cattle grid would be aesthetic enough.
https://maps.app.goo.gl/1anrXAPRE3Dp3ZFo9
https://maps.app.goo.gl/YTfAYamG55SftWay6
https://maps.app.goo.gl/AWKxr76HUzgvSqBG7
People have free access to the river and the field, any physical barrier would limit that.