SECTION II – BACKGROUND CONSIDERATIONS

Various design criteria and other considerations were used to identify and size proposed drainage modifications for inclusion in the Capital Improvement Plan (CIP). These criteria are consistent with those described in the City of Houston’s Design Manual for Wastewater Collection Systems, Water Lines, Storm Drainage, and Street Paving (Design Manual), dated October 1999. In addition to the Design Manual, other issues were considered in the identification of proposed projects to be included in the CIP. A discussion of the Design Manual and a description of these other considerations follow.

A. BASIS FOR DETERMINING IMPROVEMENTS

The proposed CIP drainage modifications (improvements) were made by identifying the storm sewer systems that were inadequate. Several factors were considered in determining the inadequacy of these systems. Such factors include design criteria in the City’s Design Manual, historical flooding, and land use patterns. The following is a description of each factor.

1. Design Criteria

The Design Manual states that storm sewer systems will be sized to convey runoff from the 2-year storm event, and that the hydraulic gradient should be below the gutter line. For development of the CIP modifications, the 2-year storm event criteria are also used. For this project, available storm sewer data included pipe size, flowline elevation, and manhole rim elevation; but no information on gutter elevations was accessible. Since the elevation of the gutter line is not known, the manhole rim elevation was used as the benchmark for the hydraulic gradient. For this project, the criterion is that the calculated hydraulic gradient should not be more than a maximum of 2 feet below the manhole rim elevation. The rim elevation is assumed to be about the same as the natural ground elevation.

2. Historical Flooding

Information on historical flooding within the City of Houston was obtained from three sources. The sources were the City Maintenance and Right-of-Way Division, FEMA, and a drainage survey specifically conducted for the Comprehensive Drainage Plan. A description of the type of information obtained from each source follows:

• City

  • Flooding information was obtained from the City’s Right-of-Way Maintenance Division, by conducting an inventory of its maintenance file records and information from an existing City database. Information included the location (street address), date, type (street, structure, ditch, etc.), and cause of the flooding incident. The depth of flooding was not included in the City information. Information concerning any actions conducted by City staff to correct the cause of flooding was also obtained. The original source of the City’s information was citizens calling the Maintenance Department to report a flooding incident.
    

• Federal Emergency Management Agency

  • The National Flood Insurance Program (NFIP) provides protection for property owners against flood-related losses by providing flood insurance. Records of insurance claims filed by policy holders are kept by FEMA. For this project, a digital file was obtained through the City from FEMA. This contained insurance claims filed on or before 1995, and filed more than once (repetitive) for the same address. The records included the street address of the claim and the date of the flooding incident. A subsequent set of repetitive loss properties was also obtained as a result of Tropical Storm Allison (June 2001).
    

• Drainage Survey

  • A drainage questionnaire was sent to each single-family residence that receives a water bill from the City of Houston. The questionnaire was mailed with the July 1996 monthly water bills to City residences. The questionnaire was sent to residents in the Kingwood area in October 1998. Approximately 51,600 completed questionnaires were returned to the City. A copy of the questionnaire used for the Kingwood area is included as Figure 1.

3. Land Use

Proposed CIP drainage improvements were identified and sized using land use conditions from 1992. The land-use data used for the CIP was developed as part of the City’s National Pollutant Discharge Elimination System (NPDES) program. The land use data consists of general land uses categorized by 14 land use types, including single-family, multi-family, commercial, industrial, public/institutional, park, undeveloped, agricultural, rangeland, forest, water, wetland, barren, and transportation/utilities. Detailed information concerning land use types is presented in HouStorm – Section IV.

FIGURE 1 DRAINAGE SURVEY FORM FOR THE KINGWOOD AREA

The City of Houston Department of Public Works and Engineering is attempting to assess the adequacy of its storm sewer system in the Kingwood area. You can assist us by completing this form and returning it within the next ten (10) days to the address shown on the reverse side. Your response is imperative as this is a survey just for the Kingwood area and not for the entire city of Houston.

DO NOT INCLUDE WITH YOUR WATER BILL.

Address:

Subdivision Name:

How long have you lived at your current address? years

Do you live in the regulatory flood plain? yes no not sure

Do you have flood insurance? yes no

Does your street experience flooding?
rarely
1-2 times per year
3-5 times per year
greater than 5 times per year

Has your street been impassable due to flooding? yes no

Has your house ever flooded? yes no

If so, how many times?

Have you had to contact city maintenance
to correct a drainage problem? yes no

Was the problem corrected? yes no

Did you experience a flooding problem
after the correction? yes no

Because your assistance is important, we thank you for your response.

Jerry King, P.E.
Director
Department of Public Works and Engineering
City of Houston
For Questions please contact the:
Customer Response Center at Phone No. 713-754-0600

ENCUESTA SOBRE DRENAJE DE ALCANTARILLADOS PARA LOS RESIDENTES DE KINGWOOD

De la Ciudad de Houston del Departamento de Obras Publicas é Ingeniería esta tratando de asesorar el sistema de drenaje pluvial mas adecuado. Usted puede ayudarnos en completar este formulario y regresarlo dentro de los próximos diez (10) días a la dirección al otro lado de esta página. Este estudio fue especialmente hecho para conocer mas mejor los conduciones de drenaje en Kingwood y no de lo demas la cuidad de Houston, por eso es imperativo que recibimos su respuesta a este esudio.

NO INCLUYA ESTA FORMA CON SU PAGO DEL AGUA.

Dirección:

Nombre de la Colonia:

¿Cuantos años ha vivido en este domicilio? Años

¿Vive en el plano de inundación regulatorio? Sí No No Estoy Seguro(a)

¿Tiene usted seguro contra inundaciones? Sí No

¿Se inunda su calle? Rara Vez
1-2 Veces por Año
3-5 Veces por Año
Mas de 5 Veces por Años

¿Ha sido su calle intransitable a causa
de inundación? Sí No

¿Alguna vez se ha inundado su casa? Sí No

¿Si es así, cuantas veces?

¿Ha hecho contacto con mantenimiento de la
ciudad para corregir problemas de dranaje
de alcantarillados? Sí No

¿Fue su problema corregido? Sí No

¿Ha experimentado problemas con inundación otra
veces después del trabajo hecho por la ciudad? Sí No

Su asistencia es importante, le damos las gracias por sus respuestas.