Rio Del Mar Flats Stormwater Drainage Improvements Project

Rio Del Mar Flats Stormwater Drainage Improvements Project


The County of Santa Cruz Rio Del Mar Flats Stormwater Drainage Improvements Project is a component of a larger project effort to construct and then operate a stormwater pump station in the Rio Del Mar Flats community (please see the area of study below). The new pump station is yet to be built, but the County has secured construction funds, design, and permits.  The County must secure funding for ongoing operations and maintenance before it can build the pump station.

CivicMic is working with the County to facilitate community outreach and public engagement with the community to consider an assessment on the property tax bill as the source of funding. This effort will determine the community's support for the project and the proposed assessment district to fund the ongoing operation and maintenance of the pump station.

Area of Study

Rio Del Mar Flats Area of Study

Drainage District Background

The Santa Cruz County Flood Control & Water Conservation District - Zone 6 was formed in 1986 and the need for fixing pre-existing drainage problems within the Rio Del Mar Flats was then identified. Unfortunately, Zone 6 does not receive a recurring annual tax base assessment but obtains funds only from a one-time development fee on net new impervious surfacing. With Zone 6 largely built out, the available declining fees are insufficient to fund construction or maintenance of a significant sized new project, such as the pump station intended to reduce the extensive rainfall ponding in this neighborhood. The County does not anticipate being able to successfully acquire at this time, a voter-approved tax assessment for the entirety of Zone 6. Thus, property owners within a smaller region more focused on those most benefiting from the stormwater pump station are being approached for the formation of an assessment district for this project.

Rio Del Mar Flats

The Rio Del Mar Flats neighborhood in the City of Aptos has a long history of repetitive flood events since development began in the area in the 1920s. The neighborhood has approximately 400 residential units, one hotel, and several small commercial buildings. The vast majority of the structures are pre-FIRM structures.

The most frequent flooding problem is ponding during rainfall-runoff events. The ponding occurs because the existing gravity flow stormwater drainage system has inadequate conveyance, in large part because of the very gentle slopes in this neighborhood which result in low flow velocities. The limited conveyance is also exacerbated by frequent impairment of conveyance from sediment and vegetative debris accumulation in the pipes. Stormwater drainage ponding flooding in the neighborhood is concentrated along Aptos Beach Drive, the adjacent side streets, and the Esplanade, which are the lowest areas in the Flats neighborhood.

Street flooding is very frequent, typically occurring several times per year. More significant damage, with ponding depths sufficient to result in building damages, occurs in local rainfall events beginning with the 2-year event.

The proposed mitigation project addresses this very frequent stormwater drainage ponding flooding problem. The proposed stormwater drainage improvement project is designed to provide the capacity to handle 10-year rainfall-runoff events, plus an additional margin of capacity.

The Rio Del Mar Flats neighborhood is also subject to overbank flooding from AptosCreek and stormwater surge flooding from the Pacific Ocean. River overbank flooding or stormwater surge flooding occurs with return periods greater than 10 years. Mitigation measures for these longer-return period flood events will be much more expensive and will have significant permitting issues. Mitigation measures for these flooding events are not included in the current proposed mitigation project.

The proposed project addresses and solves the most frequent highly-repetitive flooding problem which is ponding in the lowest part of the Rio Del Mar Flats neighborhood during local rainfall events.

Proposed Mitigation

The proposed mitigation project has two main elements, which will substantially reduce future flood damages and losses from rainfall-runoff events in Rio Del Mar Flats:

  • Construct a stormwater pump station, which will substantially increase the conveyance capacity of the stormwater drainage system; and
  • Construct a gravity flow pipe to intercept runoff flowing down the steep section of Rio Del Mar Flats at an elevation well above the Flats. This project element reduces runoff volume into the flats and complements the flooding reductions achievable by the pump station alone.

Rio Del Mart Flats Stormwater Project Survey

CivicMic is hosting an online survey to help the County of Santa Cruz determine the community's support for the stormwater drainage improvements project and the proposed assessment district to fund the ongoing operation and maintenance of the pump station.

Take the Survey!

Your participation in the Rio Del Mar Stormwater Project is very important.

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15 thoughts on “Rio Del Mar Flats Stormwater Drainage Improvements Project”

  1. The Flats area is a specific flood zone which the homeowners were aware of when they purchased in that area. This does not and should not include the beach homes on beach drive. If the flats area homeowners would like to pool together and agree to a tax to upgrade the flood prevention methods then that should be up to them. Only the areas in the flood zone due to river overflow should be included. Remove Beach drive homes from the assessment.

    1. Hi Leslie,

      We appreciate your input and have forwarded your comment to the assessment district consultant for consideration and clarification as needed.

      Pablo @ CivicMic

    2. Hi Leslie,

      I received the following response to your question from the special assessment consultant. I hope you find this helpful.

      There are two categories of benefits provided by the maintenance and operation of the drainage improvements. They are Flood Risk Mitigation and Increased Access to Property. As you have noted, there are properties in the “Flats” area that will receive Flood Risk Mitigation benefits from the maintenance and operation of the improvements. We agree that the property along Beach Drive should not be assessed for this category of benefit.

      However, there are also properties where the primary ingress and egress is through the flood risk areas. These properties receive an Increased Access to Property benefit by not having to endure travel impediments such as delays and road closures due to this repetitive flooding. In addition to being an inconvenience, these impediments can affect the provision of emergency services and potentially the ability to evacuate if required.

      Please note that all parcels will not pay the same assessment amount, the assessment considers whether or not a parcel is in the “Flats” area and receives Flood Risk Mitigation benefits (there are three levels of benefit in the “Flats” area depending on a parcel’s elevation). The assessment also considers if a parcel receives Increased Access to Property benefits. The properties along Beach Drive only receive Increased Access to Property benefits and are assessed only for that benefit which results in a much lower assessment amount than property in the “Flats” area who receive greater benefits.

      1. How much is the assessment for the Beach Drive Properties. Essentially all that is needed is clearance at the turnabout as you can come down the hill and make a uturn to beach drive. This can’t be much

        1. Hi Leslie,

          I have requested the rates per parcel from the assessment consultant and will publish them on the web map as soon as I receive them. You will be able to pull up each parcel and see the assigned assessment amount. Please click here to learn more about the upcoming community meeting where rate information will be provided. The meeting will be recorded and posted about a week after the meeting for those not able to attend.

  2. My understanding of this proposal is we are using a fossil fuel pump engine, when using an electric motor is quiet and can be backed up with a storage battery. Also the pump motor can be above ground and there is no need to build a pit and housing. Maintenance would be much less money as well. Please correct me, but I don’t understand this decision.

    1. Hi Eric,

      The pump station will use electric motors on all pumps. The electricity for normal operations will be supplied by typical PG&E service.

      The pumps are located, by necessity, underground. It is possible to have chosen motors that would be located above ground, but this would not have been as quiet in operation as motors submersed with the pumps and would have taken up additional limited space above ground level, potentially interfering with views sought to be protected as much as possible. The decision to use submersible motors was ultimately made by the sanitation design engineer, in part because submersible pumps are what is already being supplied, maintained, and trained for by the County’s sanitation crews who will maintain these pumps and motors. This familiarity and operational consistency save costs over the long-term for the maintenance.

      In the advent of a power failure, a portable diesel engine will be available; the portability provides a space and cost reduction on the amount of permanent structure having to be built. This back-up use is not expected to occur with any regularity and is also seasonal, so it is harder to justify a fully dedicated back-up installation. Possibly the future might allow on-site battery storage as back-up, but as of a few years ago when this decision was made such batteries were still costly; and the issue of dedication for a rare and seasonal use returns as a disincentive.

      I hope this helps.


  3. Beach Drive residents and their visitors have never been UNABLE to access Beach Drive when there is water on the roads of Rio Del Mar Flats. The water has never been so deep as to prevent ingress or egress. All vehicles simply drive through the curb-high water. Emergency vehicles such as police, ambulance and fire are likewise not impeded. This is an unfair tax grab against those on Beach Drive. I oppose any such tax for a water condition that County-wide taxes should pay for.

  4. On the one hand, the County and the California Coastal Commission want to place severe restrictions on how Beach Dr owners can rebuild their homes, either as a result of storm loss or just remodeling. Apparently, they want to “allow” just one rebuild per house, then you can’t do any substantial remodel again, ever! Why? Because they don’t want the houses on Beach Dr. So, they want to ruin our property values, but at the same time they want to hit us with additional taxes? We already pay huge sums in property tax due to our beach front valuations, but we don’t get any of the comprehensive police and sheriff support that we should receive based on our taxes. When is the last time you saw a sheriff patrol car drive down Beach Dr? Maybe once a month? I strongly oppose this tax. We already pay our fair share in taxes on Beach Dr. And to the County, if you don’t want us down on Beach Dr, then leave us alone for taxes too.

  5. To my knowledge, the roundabout near the beach bathrooms does not flood during the rare times Aptos Beach Drive has water on it. So for Beach Drive residents, all they have to do is drive down the hill (east) on Rio Del Mar Boulevard, make a hairpin turnaround at the roundabout, and drive east on Beach Drive.

  6. Hello,
    We own the first home on beach drive and it appears that the outflow is right next to our home. Is there a reason the outlet cannot be moved to an area that does not have any homes closer to the mouth of the river instead? Thank you

    1. Hi Sonal,

      The siting of the outfall was carefully selected in a stable area, least likely to be affected by creek meandering and wave action, with sufficient distance from existing structures. The suggested location had been heavily impacted before to the degree that the area completely eroded away so it is not suitable for siting the drainage system outfall there.

      1. Sure. However, why would our home be selected as the area that will be impacted and the sand around it eroded? Given the new and increasing restrictions around what we can and cannot do in the event that our home is destabilized, this seems like it has singled out our home for maximum impact. We do not agree with the placement of the outlet and request that it be relocated away from our home. Thank you.

  7. As the homeowners who will likely see the most impact to the stability of our home, we would like to request information that confirms this statement — “The siting of the outfall was carefully selected in a stable area, least likely to be affected by creek meandering and wave action, with sufficient distance from existing structures.”
    We would like detailed analysis performed by professionals that the distance is ‘sufficient’ and that the area is stable and unlikely to be impacted by any form of erosion due to the outlet. In addition, we would like to see reports that allow for this outlet to be places in a previously protected area. From what we understand, the vegetation in that area is protected and cannot be disturbed.
    Please know that we want there to be adequate drainage for all the homes around but given the restrictions on beach drive specifically and as new homeowners here we would just like to protect our interests.
    Thank you

  8. As a homeowner on beach island I am worried that the location of the storm drain outlet will wash away the strip of sand that protects our home. This will bring the storm surge and river flood waters right to our foundation undermining our home. Here is a video of the Jan 28th flood which almost washed away the toilet. Pumping thousands of gallons of water right at our foundation will wash away the sand. Please watch this video:

    Please help protect our home, thanks.

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