California statutes and common law provide that downhill properties must accept the natural flow and runoff from uphill properties and may in turn pass this natural flow to properties below. Natural flow includes overland surface runoff and natural channels such as creeks. Each property owner’s duty is to leave the natural flow of surface water undisturbed. Uphill landowners may not alter or concentrate the discharge of runoff from their property such that it damages downhill properties. Application of this drainage principle can be legally complex. You may need the advice of an attorney specializing in drainage law to understand your rights and responsibilities.
Drainage between private properties is a civil matter between you and your neighbor. It is not regulated by City Code. As previously noted, common law requires that you stabilize your property to accept natural flow from uphill properties, but it does not require you to accept and manage altered, concentrated discharges. We recommend that you first meet with your neighbor to look at the problem and work out corrective action. You could inform your neighbor of this information to help him or her understand the responsibilities of an uphill property owner. You may wish to consider mediation if your neighbor is not cooperative. The Peninsula Conflict Resolution Center (650-513-0330) can provide this service. If this fails, you may need to engage legal counsel to protect your property rights.
To minimize damage to your property, start by reviewing the site conditions before you purchase the property. The seller should disclose any known drainage or flooding problems but you may also want to hire a qualified inspector. Look at the property to identify wet-weather flow patterns. For example, water may flow from the street to the property if the driveway or house is below street level. Consult with a qualified engineer to assess the cost to fix the problems. If you own the property, you probably already know about the drainage problems. Your next step is to determine who is responsible for fixing these problems. Engage a qualified engineer to design a remedy if you determine that you must stabilize your property to protect it from damage or to protect downhill properties. Most drainage projects require a building or grading permit, so check with the Belmont Permit Center (650-595-7422) before starting construction.
You can discharge surface or ground water to a City street if it has a curb and gutter drainage system. You may also be allowed to construct a discharge connection to a City drain pipe in a City street or on your property. These actions all require permits so check with the Belmont Permit Center before construction. You may not discharge to the street if it does not have a curb and gutter since this can result in damage due to concentrated flow. You are also prohibited from discharging rainwater into the sanitary sewer system. Inflow of rainwater causes sewage overflows and increases sewage treatment costs and so is expressly forbidden by the City Code. Violators will be cited and may be fined.