The Corrigan subdivision is located in a large shallow bowl that suffers frequently from inadequate drainage. During major storm events over the Mary’s Creek watershed, water from the creek “backs up” into Corrigan by way of the Corrigan Ditch, overflowing into the streets since the elevations are below BFE. Not only does the Corrigan Ditch provide a path for flooding from Mary’s Creek, the floodwater flows around and across the streets throughout Corrigan. The area also floods during intense, localized rainfall due to inadequate capacity in the main outfall channel (Corrigan Ditch), inadequate storm sewer capacity, and limited flow paths for sheet flow. “Nuisance” flooding caused by heavy localized rainfall events is generally limited to street flooding for one to two hour periods. Occasionally, both types of flooding occur simultaneously, causing significant flooding.
As shown on Map 5-2, many homeowners in Corrigan have obtained NFIP flood insurance policies and several are listed by the NFIP as have received repetitive flood claims.
To address the frequent flooding in Corrigan, the City of Pearland’s Program Manager for Mobility and Drainage Program has concluded that general improvements are necessary and may cost an estimated $10-11 million. The project, which has been designed and funded in the 2001 bond election (with subsequent additional incremented funding) includes the following elements:
Diverting the rainfall runoff from north of Broadway around Corrigan by constructing a by-pass channel that will take the flow directly to Mary’s Creek;
Constructing a barrier north of Corrigan to prevent off-site sheet flow from entering Corrigan from that direction;
Realigning the Corrigan Ditch outfall into an existing pumped detention facility and retaining the internal Corrigan rainfall runoff; and
Constructing internal street and drainage improvements to provide capacity for higher intensity storm events and provide overland sheet flow paths to the Corrigan Ditch.
6.6.6 Floodplain Acquisitions
Prompted by significant flooding in 1994, which resulted in Presidential Declaration DR1041, the City initiated acquisition of a number of flood-damaged homes. A Hazard Mitigation Grant Program (HMGP) grant of $300,000 was awarded through the Texas Division of Emergency Management for the acquisition and removal of three substantially damaged properties. The City provided the 25% non-federal match.
Tropical Storm Allison (DR 1379) caused near-record flooding and damage, prompting a new effort to acquire flood-damage homes. An HMGP grant of $7,650,000 was awarded for the acquisition of 89 homes.Subsequently, the City initiated an HMGP application to “fast track” acquisition of homes damaged by the flood. Two separate acquisition and relocation programs were initiated, one by the properties located in the part of the City that is in Brazoria County. The other effort, undertaken with the Harris County Flood Control District, was for properties located the portion of the City that is in Harris County.
As a condition of the mitigation grants, the acquired lands must be retained as open space. Consequently, the City maintaining the vacant lots through a mowing contract to provide 39 mows per lot, per year. Due to this high, on-going cost, the City is exploring compatible uses by adjacent property owners in exchange for maintenance. In addition, where there are four or more contiguous lots, the City is working with the neighborhood associations to explore re-use as neighborhood parks.
6.6.7 Public-Private Partnerships
The City of Pearland has not formed any public-private partnerships that are related to natural hazards and hazard mitigation.
The City of Pearland values its open space and encourages protection of trees and wetlands in its development processes. The approval process for subdivisions within the City and the area designated as the extra-territorial jurisdiction (within 5 miles of the corporate limits) requires developers to delineate waterways, drainage structures, the boundaries of flood-prone areas (including floodways). Activity proposed within wetland areas must be approved by the U.S. Army Corps of Engineers under the authority of Section 404 of the Clean Water Act.
Open space is addressed in the subdivision ordinance:
Sec. 27-4(E) Public Use and Service Areas – the City may require up to 10% of gross area or water frontage for park, school or recreational purposes.
Sec. 27-11 Parkland Dedication – sites for park and recreation purposes to be recorded; locations to be approved by the Parks and Recreation Director (ratio of one acre of park for every 100 dwelling units). Area to be appropriate in area, shape and terrain for intended park uses. Pipeline easement shall not be considered part of park dedication; other easements or detention ponds may be acceptable. City may elect to accept a fee as alternate to dedication, in whole or in part, to maximize accessible locations.
Pearland Tree Protection and Preservation Ordinance (Ordinance No. 1108). This document was adopted July 2003. The City Council of Pearland determined that the urban forest is of great value in the maintenance of public health and welfare; the urban forest can aid in the conservation of vital energy resources and natural resources and in the preservation of the City's heritage and quality of life. Seeking to balance the benefits of protecting and preserving trees with the rights of individual property owners, the Council determined that the best approaches for accomplishing numerous benefits involves the preservation or replacement of existing trees that may be removed by the following methods: (i) avoid tree damage (including removal) whenever feasible; (ii) mitigate damage when it occurs; (iii) require on-site replacement of trees that must be removed, and (iv) require off-site replacement of trees that cannot be replaced on site, either by direct planting or through a "tree trust". Excepted activities include public utility work if it takes place in dedicated and accepted easements, right-of-way and floodways; and removal of trees which pose a hazard or harm (with appropriate documentation and approval by the City).
City Projects & Environmental Compliance
Capital projects that impact wetlands or remove trees must satisfy the same mitigation requirements imposed on private development projects.