Drainage systems for excess body fluids and associated methods are disclosed herein. A body fluid drainage system in accordance with an embodiment of the present technology, for example, can include a catheter that has an exterior surface, a proximal portion, and a distal portion opposite the proximal portion. The body fluid drainage system can further include a valve device, a pressure sensor, and a controller operatively coupled to the valve device and the pressure sensor. The valve device can include an actuator positioned over the exterior surface of the catheter. The actuator is movable between an open position that allows body fluid flow through the catheter, a closed position that at least substantially obstructs the body fluid flow through the catheter, and intermediate positions that partially obstruct the body fluid flow through the catheter. The controller can change the position of the actuator in response to a predetermined condition of the pressure sensor.