Changing the Course of the Coyote River in San Jose

Upper Silver Creek Diversion
Or
The Effluent of the Affluent

October 30, 2006

Downtown San Jose Coyote creek-side residents are facing deeper water as the Santa Clara Valley Water District plans its current “flood protection” project. Storm sewage carrying sediment and pollutants from streets, parking lots and rooftops from the upper Evergreen Valley estates has already been diverted into an artificial flume that delivers it to Coyote Creek upstream of its more natural path down Silver Creek. This storm runoff flows into Coyote Creek about eight miles upstream of the normal confluence with the lower Silver Creek, opposite the City’s old incinerator plant, now know as Watson Park.

The engineers at the City of San Jose and the Santa Clara Valley Water District (SCVWD) decided in the early 1970’s to split the Silver Creek drainage area in order to reduce the floodwaters that had for centuries flowed into a upland wetland, now enshrined, and losing most of its former natural beauty, as Lake Cunningham. Part of the natural wetlands, however, was just where the City and developers wanted to place a new state of the art shopping mall, called Eastridge. Because the City immediately began counting the enormous sales tax revenue to be gained from this new cash register, their engineers arrived with a checkbook and an offer to help the Water District staff again change the course of (in this case, not-so-mighty) rivers.

Downtown creek-side residents and the neighborhoods didn’t notice or object to this stormwater diversion project, probably because they weren’t informed about the direct impact such a decision would have on the river running behind their homes. When first constructed, the diversion structure was limited to a flow capacity of about 1000 cubic feet per second. That’s equivalent to about 646 million gallons in a day. During a flood, that is the amount of extra water in the river that wouldn’t be there if the drainage area of Silver Creek was left to its natural course through the wetlands and discharging eventually through the lower Silver Creek into lower Coyote Creek and the Bay.

During the next 10-15 years, after the diversion was installed, this upper Evergreen Valley watershed began to rapidly develop, crowned by Shea Homes’ bellwether “Silver Creek Estates” project, including its golf course and country club. As the watershed was hardened by construction of this (sub)urban development, the runoff from these seven square miles of the diverted watershed began to shed more and more runoff with every storm. Soon, water started pooling at Highway 101, when flows exceeded the capacity of the constructed bypass. The engineers were again on the spot to fix the problem. Although Shea Homes had made modest efforts to contain some of the runoff within their project area, the aggregate runoff from all the development, was now exceeding the 1000 cubic feet per second (CFS) capacity of the diversion culvert under the freeway.

The City requested the Water District to enlarge the culvert capacity below Highway 101 asking for an 84-inch diameter culvert along side the existing culvert. The District decided that it should be a 108-inch diameter culvert to convey the 1% flood from the seven square mile area. Based on this discussion, the staff brought a cost-sharing agreement to the Water District Board where they approved the project on May 24, 1994.The total project would cost $1.227 million, and the District would pay for 17 percent.

The District wanted to appear to be concerned about induced flooding from the project, and wanted the culvert partly blocked to allow less water to be channeled to the upper Coyote until downstream capacity was somehow increased to handle the full 1% flood flows of the entire Coyote watershed from above the diversion discharge. The assumption being plied here was that the 2000 CFS (646 million gallons X2 = 1.3 billion gallons per day) was significant but the slightly reduced flow (@1200 CFS) was not. It makes one wonder which engineering schools induce this kind of thinking?

The District did place a clause in the agreement with the City that indicated that this entire project could be mitigated. In Recital #9 of the agreement it states
“The CITY and DISTRICT agree to cooperate in the preparation of a study evaluating the use of alternate methods of storm water management to reduce flooding and runoff from development within the Coyote Creek watershed upstream of the culvert at Yerba Buena Road and State Route 101.”

The world has changed dramatically for water engineers, even since 1994, when this diversion project was doubled in size without concern for the immediate and measurable impacts on downstream creek-side property owners. Things like Habitat Conservation Plans and hydro-geomorphic analysis are part of the regulations that confounds simple-minded terraforming proposals like the Upper Silver Creek Diversion Project. Even with the California Environmental Quality Act being on the books since the early 70’s, the City and District engineers concocted and build this project without any real consideration it would have on Coyote Creek-side property owners in downtown. Their engineers simply declared it to be insignificant.

The State of California, acting on behalf of the Federal Government in enforcing the Clean Water Act, ordered the communities in the South Bay region to begin to use stormwater detention devices to slow the discharge of runoff into local creeks, trying to avoid both the street pollutant loading and the increased soil erosion caused by increased flow velocities. The District, as a named discharger in the runoff permit, has tried to find a role in locating strategically placed stormwater detention facilities that can contribute to better overall watershed management.

Since this activity ties the Water District closer to the well-guarded function of land use management, the District has spent many dollars and time conducting a collaborative process to communicate its needs for protecting the riparian corridors along the counties 800 miles of streams, creeks and rivers. To date, the process has completed a 130-page Water Resources Protection Manual and an 11-chapter Users Manual: Guidelines and Standards for Land Use Near Streams
These documents can be downloaded from the Water District website at HYPERLINK "http://www.valleywater.org" www.valleywater.org. Unfortunately, the outcome of the collaborative process resulted in the Water District “punting” their role as watershed steward by agreeing that the fifteen cities, and not the District, would be responsible for protecting the riparian corridors, except for the 30% of the creek-side lands owned by the District.

The Upper Silver Creek Diversion has already taken from the full use and enjoyment of the lands of the Coyote Creek-side property owners, exposing them to an annual risk of deeper flooding of their properties, without, either the City of San Jose or the Water District ever offering or paying any compensation.

But if that is not enough pain and suffering to inflict on the creek-side property owners, there’s more at the door. The Water District is currently holding public meetings for the purpose of collecting input on a channeling project to keep more overflows from leaving the banks of the Coyote Creek, by somehow raising the capacity of the main channel to up to 17,000 CFS. The justification for this project, among others, is to remove other parcels of land not on the creek from the danger of flooding, since these properties were built in natural flood bypass channels, which have been clearly mapped by FEMA and available to land use planners for years. Since the District does not protect the community from flooding by advising the City not to build in these areas, they are now pressured by such property owners to protect them from flooding and relieve them from the burden of paying flood insurance.

FEMA Sidebar:
Flood insurance premiums are paid to FEMA, acting as the federal agency managing the National Flood Insurance Program. And it is FEMA regulations that allow homes to be built on the floodways, and then to mandate most lenders to require flood insurance. Despite FEMA being the insurer of many of the properties that flooded, FEMA joined in a local civil action against the City of San Jose and the Water District. FEMA initiated a subrogation proceeding to recover its emergency aid expenditures made during the 1983 flood in Alviso, claiming, as did the plaintiff/victims, that the flood was caused by the City of San Jose. A $300 million suit was settled for $13 million for the flood victim-residents and FEMA. FEMA walked off with $3million of the suit, nearly a quarter of the settlement funds.


This Water District’s current project for Coyote Creek intends to spend tens of millions of dollars in parcel taxes collected under the Clean Safe Creeks and Natural Flood Protection Program passed by two-thirds of the voters in the County in 2000. This program will collect a total of $350 million county-wide over 15 years and expects to spend $35 million on the Coyote Creek, far less than what is probably needed to buy the land, structures and build levees and new bridges to accomplish their goals.

The Water District and the City of San Jose should first confront and resolve the damages already occurring to the Coyote Creek-side landowners before they jointly or separately decide to worsen the condition of introducing additional floodwaters into the existing banks of the creek.