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Background
The Adobe Creek problem had existed for years before the major project to resolve it finaly succeeeded in getting something done. The work to define the solution took place approximately between 2004 and 2009. The main problem had its origins in the beginnings of suburban development in this area (early 1900’s) and weas largely caused unwittingly by San Francisco residents building week-end retreats “in the country” in what eventually became Los Altos and Los Altos Hills. A prime area for this was in and around what is today Edith Park – close to the railway for ease of access from and to “the city” but nevertheless “rural”. A prime spot for this was along the banks of Adobe Creek - nice to have a creek at the bottom of the yard – with even the occasional fish in it. Great for kids to play in (Today’s Shoup Park had its beginnings this way) But the creek had achieved a “balance” in terms of how wide and deep the channel was – erosion versus silt deposit washed down from the hills - over the eons. But this balance changed with all the “hardscape” that started to be built in the rain-catchment area of the creek – roofs of houses, barns, tennis-courts, driveways, roads, etc. The surge of water in the creek that would result from a rain-storm suddenly became much more sudden and voluminous because much more of rain-water never got a chance to either sink in the ground or trickle slowly via puddles and rivulets through the vegetation to the creek. On the contrary, it was caught in gutters and sent directly into the creek assisted by roadside gulleys and culverts to dump directly into the creek. These sudden lager water surges changed the balance of the creek bed so that there was much more erosion going on. People living along the banks of the creek noticed bits of their backyards washing away… So they took corrective action. One neighbor might install some redwood planks along the edge of the creek in his yard to hold back the erosion… But changing the character of the creek bank from vegetated dirt to redwood planks just speeded the water even more – exacerbating the erosion problem for the neighbor a little further downstream. So that neighbor in turn lined the creek bank in his backyard with a small wall of concrete cinder-blocks to protect his backyard - which speeded up the water even more… So the next neighbor, in desperation, lined the whole of the part of the creek that went through his backyard with gunnite – the stuff they make swimming pools out of. And so the once-pleasant rural creek became wider, deeper, steeper, and all contained in a concrete gulch all the way down to the edge of the bay… Projects to tackle the situation were planned and initiated and failed to achieve anything useful over a period of decades. This was partly because the responsibility for the creek was spread over so many different “jurisdictions” that nobody was in charge or had the overall authority to do anything. There were two city governments (Los Altos and Los Altos Hills), a number of residents owning creekside property – also spread across the two cities and with different zoning laws, the the Santa Clara County Valley Water District, as well as a host of other government agencies all with a finger in the pie – Fish and Game, Water Quality, EPA, Corps of Engineers… you get the idea. A bunch of outfits, each being responsible for a different aspect, that might be involved in any potential work on the creek. And all of these had to be in agreement and sing in unison in order to be able to do anything to the creek to fix matters. So a “project” was initiated that involved a “collaborative” with members from all interested parties. An independent professional "Facilitator" was initialy hired to run the meetings, but this lasted for exactly one meeting. An alternative facilitator was "volunteered" by a party or parties unknown, and I fulfilled this role as well as "keeper of the working documents" for about six years until project completion. They met approximately once a month for around four years - and out of this, agreement was reached on how to “restore” the creek. This involved re-routing and grading the creek and rebuilding and re-engineering the banks. The new creek-bed was designed to maintain an even gentle slope (removing some rapids and even waterfalls that had developed over the years) as well as smooth out some curves to minimize erosion from “peak events”. The Role Played by the San Francisco Dusky-Footed Wood-Rat A condition imposed by one of the stakeholders involved conservation and habitat restoration for an animal called “The San Francisco Dusky-Footed Wood Rat”. We were informed by the biologist that this was not really a rat at all, neither was it officially classified as endangered – however it was listed by the relevant agency as “Being of interest” and so special accommodations had to be made to “move” these animals by means of relocating their homes downstream little way. This was achieved (amongst other measures) by creating nooks and crannies in the new creek banks as well as in the banks downstream. This was achieved by inserting short lengths of clay pipe in the banks of the creeks to provide shelter for the various fauna inhabiting the creek. Some Technicalities we learned - the Thalweg and the Meander The "Thalweg" of a creek is the path that a trickle of water would take along the lowest part of the creek-bed. The banks of the creek (from the "thalweg" up to "top-of-bank") may be a shallow slope or may be very steep. The bank on one side of the creek may be steep, but a gentle slope on the other - in which case the thalweg (where the greatest volume of flow in the creek occurs) would not necessarily be in the center of the creek between the two banks - as might be assumed by a casual passer-by or somebody looking at an aerial photograph. This is particularly true in the case of a “Meander”. Where the creek curves first in one direction and then another, the water exerts more force on the outside of the curve compared to the inside of the curve. Consequently there tends to be more erosion on the outside of a curve, a lot of the erosion products (silt) may then be deposited on the inside curve of the next meander where the water exerts less force. This means that if the banks of a creek are not strong enough to withstand erosion, a small meander will grow bigger, as will the next meander downstream, as will… and so on. So what might have been a relatively simple straight-flowing stream over the centuries, may transform its course over the years into a series of ever wider meanders due to the impact of civilization occupying the area along its banks – as a result of the “peak” flow of water through the stream being increased over the years. This is what happened to the section of Adobe Creek starting roughly where it passes Foothill College and all the way to where it crosses under Foothill Expressway on its way to the Bay. The lower extent of the creek beyond this (e.g. where it goes under El Camino) has long since had its banks concreted over to control any further erosion. |
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The following pictures give some chronological views of the work as it progressed
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| "Richard" - a creekside resident who played a major role in the collaborative, a focal point for the "Los Altos" group of residents |
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| "Tony" who worked for the Santa Clara Valley Water District - and who played a leading role as part of the collaborative in bringing the project to a successful conclusion |
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 | Click here to go to pictures of the creek as it was before work started | |||
| Click here to go to pictures of the creek three years after completion | |||